(. x y y x f y = f(x y x y = y(x y x y dx = d dx y(x = y (x = f (x y = y(x x ( (differential equation ( + y 2 dx + xy = 0 dx = xy + y 2 2 2 x y 2 F (x, y = xy + y 2 y = y(x x x xy(x = F (x, y(x + y(x 2 F (x, y 2 x, y = F (x, y ( dx y = y(x ( I (solution y (x = F (x, y(x x I ( I I C y = Ce x R = (, dx = y (2
2.2 ( y = y(x ( (x 0, y 0 y (x 0 (y 0 = y(x 0 y = y(x ( y (x 0 = F (x 0, y(x 0 = F (x 0, y 0 (x 0, y 0 ( (x 0, y 0 F (x 0, y 0 xy (x, y (, F (x, y ( ( xy (2 y = Ce x C ( y = Ce x (x 0, y 0 (y 0 = Ce x 0 Ce x 0 = y 0 (, y 0 0.75 0.5 0.25 0.5 - -0.5 0.5.5 2-0.25-0.5 - -0.5 0.5.5 2-0.5-0.75 - -.3 x, y x y f(x, y C f(x, y = C C C C ( C f(x, y = e x y e x y = C y = Ce x C f(x, y = C : C C C 2 f(x, y = C f(x, y = C 2 f(x, y = C = C 2 (x, y C C 2 x y ( f(x, y = C y x y
3 y = y(x ( y(x C C y(x y = y(x e x y = C y = y(x x e x x y + e dx = e x y(x + e x y (x = 0 ( y(x y y = y(x C (2 C (2 C ( y = Ce x (2 y = Ce x C f(x, y = C x y = y(x ( xy = C (C 0 (2 x + y2 2 = C (3 x 2 2 + y2 = C (C > 0 0.75 0.75 0.75 0.5 0.5 0.5 0.25 0.25 0.25 - -0.75-0.5-0.25 0.25 0.5 0.75-0.25 - -0.75-0.5-0.25 0.25 0.5 0.75-0.25 - -0.75-0.5-0.25 0.25 0.5 0.75-0.25-0.5-0.5-0.5-0.75-0.75-0.75 - - - 2 2. ( F (x, y x y F (x, y = g(xh(y h(y 0 dx = g(xh(y (3 h(y dx = g(x x ( g(x dx = h(y dx dx = y (x h(y(x dx = h(y
4 g(x G(x, C = C 2 C h(y H(y C, C 2 H(y + C = G(x + C 2 H(y G(x = C (3 y = y(x (C h(y = 0 y y 0 y(x = y 0 (3 x + y2 2 = C (2 dx = y y = y(x (x, y y dx = y y = dx c log y = x + c y = ±e x+c = ±e c e x = Ce x (C = ±e c C 0 y = 0 C = 0 0.75 0.5 0.25 - -0.5 0.5.5 2-0.25-0.5-0.75 - x + y2 2 = C y = Ce x
5 2 t x(t x (t x(t k x (t = kx(t dx dt = kx dx x = k dt x(t = Ce kt x(0 = C t x( = Ce k = 2C e k = 2 t Ce tk = C(e k t = C2 t 3 ( α ( β ( γ ( k t ( x(t dx dt = kx k k x(t = Ce kt C = x(0 e kt = t T 2 e kt = log 2 T = k T 2 k x(t = C(e kt t T = C2 t T 3 8 β γ 3 t 3 x(t = C2 t 8 37 30 β γ 37 t 37 x(t = C2 t 30 4 ( t x(t a x (t x(t a (x(t a > 0 x (t < 0 k dx dt = k(x a x (t = k(x(t a dx x a = k dt log x a = kt + c x = x(t = a ± e c e kt = a + Ce kt (C = ±e c.
6 2 20 (t = 0 00 5 80 5 3 ( dx = y2 (2 dx = y (3 dx = xy (4 dx = e y 5 x km y(x ( k > 0 k x y(t dt = y(x ( x ky(x = y (x y(x = Ce kx 000 km 900 C = 000, e k = 0.9 y(x = 000 0.9 x 6 x(t a x (t x(t a x(t a x(t k > 0 dx dt = kx(a x ( dx x(a x = k dt = kt + c dx x(a x = ( a x + dx = a x a log x a x ±e ac = C x a x = Ceakt x = aceakt + Ce akt = a + C e akt t a C C 0 x = a a =, k =
7 0.8 0.6 0.4 0.2 2 3 4 5 7 m t v(t mv (t mg (g v(t kv(t (k mv (t = mg kv(t m mg kv dv = dt = t + c m k log mg kv = t + c C = ±e ck/m mg kv = Ce kt/m v = v(t = k (mg Ce kt/m v(0 = 0 C = mg v(t = mg k ( e kt/m v(t t mg k 4 ( dx = xy2 (2 dx = y2 y 2 (3 dx = y2 + (4 dx = ex+y 2.2 dx = F (x, y
8 y = y(x x = x 0 y(x y 0 dx = F (x, y, y(x 0 = y 0 y = y(x x t t = t 0 ( 8 t = 0 t x = x(t dx dt = kx, x(0 = C x(t = Ce kt x(0 = C = x(t = e kt x(t t 9 dx = y2, y(0 = y = y(0 = C = x + C y(x = x x = (, (x > y = y(x x < x > 5 ( (3 (5 (7 dx = xy, y(0 = (2 dx = y2, dx = y2, y(0 = 0 (4 dx = y2 +, y(0 = (6 dx = y2 y 2, y(0 = 2 (8 y(0 = dx = xy2, y(0 = dx = e y, y(0 = 0 dx = ex+y, y(0 =
9 2.3 ( a(x, b(x y = y(x dx = a(xy + b(x (4 y b(x = 0 ( dx = a(xy a(x A(x c log y = a(x dx = A(x + c C = ±e c y = Ce A(x C C(x y = C(xe A(x (4 (C (x + A (xc(xe A(x = a(xc(xe A(x + b(x C (x = b(xe A(x ( y(x = C(xe A(x = b(xe A(x dx e A(x (5 (5 ( y (x = b(xe A(x dx A (xe A(x + b(xe A(x e A(x = a(xy + b(x (5 (4 (4 (5 y = y(x (4 z(x = e A(x y(x z (x = A (xe A(x y(x + e A(x y (x = a(xe A(x y(x + e A(x {a(xy(x + b(x} = b(xe A(x z(x = b(xe A(x dx ( y(x = z(xe A(x = b(xe A(x dx e A(x (4 (5 0 = 2xy + ex2 dx dx = 2xy
0 y = Ce x2 C C(x y = C(xe x2 dx 2xy = C (xe x2 = e x2 C (x = C(x = x + C (C y(x = (x + Ce x2 y(0 = 0 C = 0 y = xe x2 t E(t I(t R L LI (t + RI(t = E(t di dt = R L I + E(t (6 L ( I(t = E(te R L t dt e R L t L I(t (i E(t = E ( ( ( I(t = Ee R L t dt e R E L t = L R e R L t + C e R L t = E R + R Ce L t (C I(0 = 0 ( 0 C = E/R I(t = E R ( e R L t (ii E(t = E cos ωt (E, ω C(t = E e R L t cos ωt dt = E ( L L Re e ( R L +iωt dt ( = E L Re e ( R L +iωt R + iω + C = E e ( R L t R cos ωt + ω sin ωt L + C L R 2 L + ω L 2 2 I(t = E L R cos ωt + ω sin ωt L + Ce R R 2 + ω L 2 L t R cos ωt + Lω sin ωt = E R 2 + L 2 ω 2 2 + Ce R L t
(C I(0 = 0 C = ER/(R 2 + L 2 ω 2 I(t = E R(cos ωt e R L t + Lω sin ωt R 2 + L 2 ω 2 E = L = R = ω = E(t ( I(t ( ( (i, (ii 0.8 0.75 0.5 0.6 0.25 0.4-0.25 2.5 5 7.5 0 2.5 5 7.5 20 0.2-0.5-0.75 2 4 6 8 0 - Euler i = x e ix = exp(ix = (ix n n=0 n! (7 x (7 i 2k = ( k cos x sin x Taylor e ix = (ix n n=0 n! = k=0 (ix 2k (2k! + (ix 2k+ (2k +! k=0 = cos x + i sin x e ix = cos x + i sin x. Euler α = a + bi (a, b R a = Re α b = Im α cos x = Re e ix, sin x = Im e ix x, y e x+iy = exp(x + iy = e x e iy = e x (cos y + i sin y e x +iy e x 2+iy 2 = e (x +x 2 +i(y +y 2 α (α 0 d dx eαx = αe αx, e αx dx = eαx α + C (C
2 ( α = a + bi (a, b R e αx = e ax (cos bx + i sin bx ( e e ax αx cos bx dx = Re α + C, ( e e ax αx sin bx dx = Im α + C (C 2 6 ( dx = y x (2 dx = y + x2 (3 7 ( (3 dx = xy + e x2 /2 dx = y x, y(0 = 0 (2 dx = y + x2, y(0 = dx = xy + /2 e x2, y(0 = 0 8 E(t = Ee at (E, a I(0 = 0 I(t E = L = R =, a = 2 t 0 I(t I(t 3 2 a(x, b(x, f(x y = y(x dx + a(x + b(xy = f(x 2 dx 2 a(x, b(x a, b dx + a + by = f(x (8 2 dx 2 3. f(x = 0 dx + a + by = 0 (9 2 dx
3 y = y(x R = (, x (9 y(x R : (9 y (x = ay (x by(x (0 y(x 2 (0 y (x y(x 3 (0 2 y(x 4 y(x (9 R C (R x, x 2 + a e ax, sin ax, cos ax C (R y(x z(x C (R a b ay(x + bz(x C (R C (R R C (R C (R D = d dx Dy(x = d dx y(x = y (x y(x, z(x C (R a, b R (y(x C (R D(ay(x + bz(x = ady(x + bdz(x D C (R C (R R D 2, D 3,... D 2 y(x 2 y (x D 0 = I (, D, D 2 C (R C (R P (D = D 2 + ad + bi (a, b R C (R C (R 2 (differential operator P (Dy(x = y (x + ay (x + by(x (9 P (D : C (R C (R (kernel Ker P (D = {y(x C (R P (Dy(x = 0} C (R Ker P (D R C (R, C (C α = a + bi (a, b R e αx = e ax (cos by + i sin by
4 C (R, C y(x z(x C (R, C α, β αy(x + βz(x C (R, C C (R, C C C (R, C C (R, C D = d dx Dy(x = d dx y(x = y (x (y(x C (R, C y(x, z(x C (R, C α, β C D(αy(x + βz(x = αdy(x + βdz(x D C a,... a m C Q(D = D m + a D m + + a m D + a m I (a,..., a m C C (R, C C (R, C C (m (differential operator Ker C Q(D = {y(x C (R, C Q(Dy(x = 0} Ker C Q(D C 2 P (D = D 2 + ad + b D λ P (λ = λ 2 + aλ + b P (D (9 (characteristic polynomial (2 P (λ = 0 α, β λ P (λ P (λ = λ 2 + aλ + b = (λ α(λ β D αi D βi y(x C (R, C (D αi(d βiy(x = (D αi(y (x βy(x = D(y (x βy(x α(y (x βy(x = y (x (α + βy (x + αβy(x = y (x + ay (x + by(x = P (Dy(x P (λ 2 P (D D αi D βi α β
5 P (λ = (λ α(λ β α β Ker C P (D = Ker C (D αi Ker C (D βi ( P (Dy(x = 0 y(x C (R, C y(x = y (x + y 2 (x, (D αiy (x = 0, (D βiy 2 (x = 0 y (x, y 2 (x C (R, C y (x, y 2 (x C (R, C (D αiy (x = 0 (D βiy 2 (x = 0 y(x = y (x + y 2 (x P (Dy(x = 0 : y(x Ker C P (D = (λ α (λ β β α β α I = (D αi (D βi ( β α β α y (x = (D βiy(x = β α β α (y (x βy(x, y 2 (x = (D αiy(x = β α β α (y (x αy(x (D αiy (x = (D αi(d βiy(x = P (Dy(x = 0, (D βiy 2 (x = (D βi(d αiy(x = P (Dy(x = 0 y (x Ker C (D αi, y 2 (x Ker C (D βi ( y(x = Iy(x = (D αiy(x β α β α (D βiy(x = y (x + y 2 (x y (x, y 2 (x y (x y 2 (x z (x Ker C (D αi z 2 (x Ker C (D βi y(x = z (x + z 2 (x u(x := y (x z (x = z 2 (x y 2 (x Ker C (D αi Ker C (D βi (:= ( u(x = Iu(x = (D αiu(x (D βiu(x = 0 β α β α z (x = y (x, z 2 (x = y 2 (x y (x y 2 (x
6 2 α = a + bi (a, b R C D αi : C (R, C C (R, C Ker C (D αi C (R, C C e αx = e ax (cos bx + i sin bx : y(x C (R, C z(x = e αx y(x y(x = e αx z(x (D αiy(x = y (x αy(x = αe αx z(x + e αx z (x αe αx z(x = e αx z (x (D αiy(x = 0 z (x = 0 z (x = 0 z(x y(x Ker C (D αi C y(x = Ce αx 2 P (λ = (λ α(λ β α β C P (D : C (R, C C (R, C Ker C P (D C 2 e αx e βx P (Dy(x = 0 y(x C (R, C y(x = C e αx + C 2 e βx C, C 2 y(x P (Dy(x = 0 α = β 3 α Ker C (D αi 2 = {y(x C (R, C (D αi 2 y(x = 0} C 2 e αx xe αx : y(x C (R, C z(x = e αx y(x 2 (D αi(e αx z(x = e αx z (x (D αi 2 y(x = (D αi(d αi(e αx z(x = (D αi(e αx z (x = e αx z (x (D αi 2 y(x = 0 z (x = 0 z (x = 0 z (x = C z(x = C x + C 2 C 2 z(x = C x + C 2 z (x = 0 Ker C (D αi 2 = {(C x + C 2 e αx C, C 2 C} y(x = (C x + C 2 e αx y(0 = C 2 y( = (C + C 2 e α C C 2 e αx xe αx Ker C (D αi 2 (9
7 a, b P (D = D 2 +ad+bi λ 2 +aλ+b = 0 3 a 2 4b > 0 α, β P (Dy(x = 0 y(x C, C 2 y(x = C e αx + C 2 e βx y(x C, C 2 C, C 2 e αx e βx y(x y(x y(0 = C + C 2 y( = C e α + C 2 e β C, C 2 C C 2 2 P (λ = 0 α, β P (Dy(x = 0 y(x Ker P (D R 2 e αx e βx P (Dy(x = 0 y(x C (R C, C 2 y(x = C e αx + C 2 e βx 2 dx 2 dx 2y = 0 λ 2 λ 2 = (λ 2(λ + = 0 C, C 2 y(x = C e 2x + C 2 e x a 2 4b = 0 α α = a 2 3 P (Dy(x = 0 y(x C, C 2 y(x = C e αx + C 2 xe αx y(x C, C 2 C, C 2 e αx xe αx y(x y(x y(0 = C y( = (C + C 2 e α C, C 2 C C 2 3 P (λ = 0 0 α P (Dy(x = 0 y(x R 2 e αx xe αx P (Dy(x = 0 y(x C (R C, C 2 y(x = C e αx + C 2 xe αx
8 3 dx + 2 2 dx + y = 0 λ 2 + 2λ + = (λ + 2 = 0 C, C 2 y(x = (C x + C 2 e x a 2 4b < 0 α, β λ 2 + aλ + b = (λ α(λ β α β β = α p, q α = p + qi e αx = e px+iqx = e px e iqx = e px (cos qx + i sin qx P (Dy(x = 0 y(x C, C 2 y(x = C e αx + C 2 e βx a, a 2, b, b 2 C = a + ib, C 2 = a 2 + ib 2 α β p, q α = p + iq, β = p iq (q > 0 y(x = C e αx + C 2 e βx = (a + ib e px (cos qx + i sin qx + (a 2 + ib 2 e px (cos qx i sin qx = e px {(a + a 2 cos qx + ( b + b 2 sin qx} + ie px {(b + b 2 cos qx + (a a 2 sin qx} y(x a = a 2, b + b 2 = 0 y(x = e px (2a cos qx 2b sin qx C = 2a, C 2 = 2b y(x = e px (C cos qx + C 2 sin qx (2
9 4 P (λ = 0 p, q (q > 0 α = p + iq, β = p iq P (Dy(x = 0 y(x R 2 e px cos qx e px sin qx P (Dy(x = 0 y(x C (R C, C 2 y(x = e px (C cos qx + C 2 sin qx 4 dx 2 + 4 dx + 5y = 0 λ 2 + 4λ + 5 = (λ + 2 i(λ + 2 + i = 0 ( 2 ± i C, C 2 y(x = e 2x (C cos x + C 2 sin x 5 m 0 k x t x = x(t q = (k m d 2 x dt 2 + q2 x = 0 λ 2 + q 2 = (λ iq(λ + iq = 0 C, C 2 x(t = C cos qt + C 2 sin qt q 2π q 9 ( (4 dx 2 dx 6y = 0 (2 4d2 y dx 2 4 dx 3y = 0 (3 dx 2 + 2 dx = 0 dx 2 + 6 dx + 9y = 0 (5 dx 2 + 4y = 0 (6 2d2 y dx 2 + 2 dx + y = 0 3.2 (9 x y(x x y(x y (x
20 6 y = y(x dx 2 dx 2y = 0 y(0 =, y (0 = 0 C, C 2 y(x = C e 2x + C 2 e x y(0 = C + C 2 =, y (0 = 2C C 2 = 0 C = 3, C 2 = 2 3 y(x = 3 e2x + 2 3 e x 7 5 x(0 0 x (0 0 d 2 x dt 2 + q2 x = 0, x(0 =, x (0 = 0 x = x(t t x(t = cos qt x 0, y 0, y dx 2 + a dx + by = 0, y(x 0 = y 0, y (x 0 = y (3 y = y(x ( w(x = y(x + x 0 w(x w(0 = y(x 0 = y 0, w (0 = y (x 0 = y x 0 = 0 a 2 4b > 0 λ 2 + aλ + b = 0 2 α, β y(x = C e αx + C 2 e βx y(0 = C + C 2 = y 0, y (0 = αc + βc 2 = y ( ( ( C = α β C 2 y 0 y
2 β α = 0 C C 2 a 2 4b < 0 λ 2 + aλ + b = 0 2 p ± iq y(x = e px (C cos qx + C 2 sin qx y(0 = C = y 0, y (0 = pc + qc 2 = y C q 0 C 2 a 2 4b = 0 α y(x = (C x + C 2 e αx y(0 = C 2 C 2 y (x = α(c x + C 2 e αx + C e αx y (0 = C + αc 2 C 8 t x = x(t x(t d 2 x dt 2 + adx dt + bx = 0, x(0 =, x (0 = 0 a b ( x(t x(t ( a 2 4b < 0 q = 2 4b a2 x(t = e a 2 t ( cos qt + a 2q sin qt. ( (2 a 2 4b = 0 x(t = e a 2 t + a. 2 t (3 a 2 4b > 0 λ 2 + aλ + b = 0 2 α, β x(t = β α (βeαt αe βt. b = 4, a =, 4, 5 y(x 0.8 0.8 0.8 0.6 0.6 0.6 0.4 0.4 0.4 0.2 0.2 0.2-0.2 2 3 4 5 6-0.2 2 3 4 5 6-0.2 2 3 4 5 6-0.4-0.4-0.4
22 0 ( dx 2 dx 6y = 0, y(0 = 0, y (0 = (2 4 d2 y dx 4 2 dx 3y = 0, y(0 =, y (0 = 2 (3 dx + 2 2 dx = 0, y(0 =, y (0 = (4 dx + 6 2 dx + 9y = 0, y(0 =, y (0 = 2 (5 dx + 4y = 0, 2 y(0 = 0, y (0 = (6 2 d2 y dx 2 + 2 dx + y = 0, y(0 =, y (0 = 3.3 f(x dx + a + by = f(x (4 2 dx y = y(x (4 y = y 0 (x y(x (4 y = y (x y (x = y(x y 0 (x dx + a + by = 0 (5 2 dx y = y (x (5 y(x = y 0 (x + y (x (4 = + (5 (4 (Heaviside D D C (R, C I 2 P (D = a 0 D m +a D m + +a m D +a m f, u C (R, C u(x = P (D f(x P (Du(x = f(x
23 u(x P (D v(x = f(x u(x v(x Ker P (D P (D u(x P (D f(x mod Ker P (D Ker P (D Ker P (D = (4 9 u(x = D f(x u (x = f(x u(x = f(x dx u(x 20 α u(x = D α f(x u (x αu(x = f(x u(x = e αx e αx f(x dx 4 α, β, γ C f(x C (R, C = Ker (D α(d β ( (D α(d β f(x = ( D α D β f(x (2 (3 D α (eγx f(x = e γx D + (γ α f(x (D α(d β f(x = α β : ( u(x ( D α f(x D β f(x (α β (D αu(x = f(x (D β((d αu(x = f(x. D β ((D α(d βu(x = ((D β(d αu(x = (D β((d αu(x = f(x. (2 v(x = f(x D + (γ α (D α(e γx v(x = (e γx v(x αe γx v(x = e γx (v (x + (γ αv(x = e γx (D + (γ αv(x = e γx f(x.
24 D α (eγx f(x = e γx v(x = e γx D + (γ α f(x. (3 u(x ((D α(d βu(x = { ( (D β (D α α β D α f(x ( } (D α (D β D β f(x (3 = {(D βf(x (D αf(x} = f(x α β 5 α 0 f(x ( D α f(x = α + α D + 2 α 3 D2 + f(x = α f(x α 2 f (x α 3 f (x f(x k D k+ f(x = f (k+ (x = 0 : t k ( t( + t + + t k = t k+ t D α ( α ( D + α D + + α k Dk = Dk+ αk+ f(x k D k+ f(x = 0 ( α ( D + α D + + α ( k Dk f(x = Dk+ f(x = f(x αk+ ( (D α α α D 2 Dk f(x αk+ = ( α ( D + α D + + α k Dk f(x = f(x ( D α f(x = α + α D + + 2 Dk f(x αk+ D k+ f(x = D k+2 f(x = = 0
25 4 ( 20 (4 ( D α D β f(x = (e βx e βx f(x dx D α ( = e αx e (β αx e βx f(x dx dx 2 (4 f(x f(x = p(xe cx (p(x c (4 4 (2,(3 5 2 dx 2 dx 2y = x λ 2 λ 2 = (λ 2(λ + = 0 P (D = D 2 D 2 = (D 2(D + 4 (3 5 P (D x = 3 ( D 2 x D + x = ( 3 2 + 4 D + 8 D2 + = ( 3 2 x + 4 3 (x = 2 x + 4 C, C 2 x 3 ( D + D2 x 22 y(x = C e 2x + C 2 e x 2 x + 4 dx 2 dx 2y = x2 e x P (D = D 2 D 2 = (D 2(D +
26 4 (3 (2 5 P (D (x2 e x = ( 3 D 2 (x2 e x D + (x2 e x = 3 ex ( D x2 D + 2 x2 = ( 3 ex + D + D 2 + x 2 + ( 3 ex 2 + 4 D 8 D2 + = 3 ex (x 2 + 2x + 2 + ( 3 ex 2 x2 + 2 x 4 = (C, C 2 ( 2 x2 2 x 3 e x 4 y(x = C e 2x + C 2 e x ( 2 x2 + 2 x + 3 e x 4 x 2 23 dx 2 + y = (x + 2 ex dx (D ((x + 2 ex = ( D D ((x + ex = (e x D D (x + = ( e x ( D 2 x2 + x = e x ( ( 6 D 2 x2 + x = e x x3 + 2 x2 (C, C 2 y(x = ( 6 x3 + 2 x2 + C x + C 2 e x 24 dx 2 2 dx + y = xe x 4 (,(2 5 (D 2 (e x = ( D D (e x x = ( e x D D 2 x = (e ( x 2 D 4 D x = ( (e x D 2 x 4 ( = e x D 2 2 x = e ( x 2 4 4 ( D 2 x 4 = (x + e x 4
27 (C, C 2 y(x = (C x + C 2 e x + (x + e x 4 f(x = ce γx (c P (λ 0 6 P (D = D 2 + ad + b γ P (De γx = P (γe γx P (γ 0 P (D eγx = P (γ eγx. : De γx = γe γx P (De γx = γ 2 e γx + aγe γx + be γx = P (γe γx ( P (γ 0 P (D P (γ eγx = e γx P (D eγx = P (γ eγx. 25 dx 2 2 dx + y = e x P (D = D 2 2D +, P ( = 4 0 6 y(x = P (D e x = P ( e x = 4 e x P (λ = (λ 2 C, C 2 y(x = (C x + C 2 e x + 4 e x f(x = p (xe a x + + p m (xe a mx (p (x,..., p m (x P (Dy j (x = p j (xe a jx y j (x j P (D P (D(y (x + + y m (x = f(x
28 26 dx + 2 dx = e x + 2e 2x P (D = D 2 + D = D(D + P (Dy (x = e x y (x P ( = 0 6 y (x = P (D e x = D e x D + e x = e x D e x D = e x ( + D + D 2 + e x x = (x + e x P (Dy 2 (x = 2e 2x y 2 (x P ( 2 = 2 6 y 2 (x = P ( 2 2e 2x = e 2x y(x = y (x + y 2 (x = (x + e x + e 2x y(x = C e x + C 2 (x + e x + e 2x = ( x + C e x + e 2x + C 2 C, C 2 C = C ( (3 dx 2 + dx 6y = x (2 dx 2 2 dx = xe2x dx 2 2 dx + y = x + (4 dx 2 + dx 6y = e 2x + x (4 f(x f(x = p(xe ax cos bx f(x = p(xe ax sin bx (p(x a, b f(x = p(xe (a+ibx (4 z(x P (D(Re z(x = Re (P (Dz(x = Re (p(xe (a+ibx = p(xe ax cos bx, P (D(Im z(x = Im (P (Dz(x = Im (p(xe (a+ibx = p(xe ax sin bx 27 dx 2 dt 2 + 2dx dt + 2x = cos ωt, x(0 = x (0 = 0. 8 a = 2, b = 2 ω > 0 cos ωt cos ωt = Re(e iωt d 2 z dt + 2dz 2 dt + 2z = eiωt
29 z = z(t x(t = Re z(t D = d dt P (D = D 2 + 2D + 2 P (iω = 2 ω 2 + 2iω 0 6 z(t = P (iω eiωt = 2 ω 2 + 2iω eiωt = 2 ω2 2iω e iωt 4 + ω 4 x(t = Re z(t = 2 ω2 2ω cos ωt + sin ωt 4 + ω4 4 + ω4 ± i C, C 2 x(t = e t (C cos t + C 2 sin t + 2 ω2 2ω cos ωt + sin ωt 4 + ω4 4 + ω4 x(0 = x (0 = 0 x (t = e t ( C cos t C 2 sin t C sin t + C 2 cos t ω(2 ω2 sin ωt + 2ω2 cos ωt 4 + ω 4 4 + ω4 C = ω2 2 4 + ω 4, C 2 = 2 + ω2 4 + ω 4 x(t = 4 + ω 4 e t {(ω 2 2 cos t (2 + ω 2 sin t} + 2 ω2 2ω cos ωt + sin ωt 4 + ω4 4 + ω4 e t t 0 a(ω (2 ω 2 a(ω = 4 + ω 4 2 + ( 2 2ω = 4 + ω 4 4 + ω 4. a(ω ω lim ω a(ω = 0 ω = π, ω = 2π x(t x x t t 28 dx + 2 + 2y = x sin x 2 dx d 2 z dx + 2 dz + 2z = 2 xeix dx
30 z = z(x P (D = D 2 + 2D + 2 P (λ = (λ + i(λ + + i z(x = P (D (xeix = ( 2i D + i (xe ix D + + i ( = eix 2i D + x D + + 2i = eix 2i eix ( D + x 2i = eix eix (x 2i 2i y(x = Im z(x = ( + 2i ( + 2i x ( + 2i 2 y(x = e x (C cos x + C 2 sin x + 2 ( + 2i D + ( 2 2i = 5 x + ( 2 5 x + 4 ( cos x + 25 5 x 2 sin x 25 x 2 + 4i 25 e ix ( 2 5 x + 4 ( cos x + 25 5 x 2 sin x 25 ( (3 dx 2 + 4 dx + 5y = cos x (2 dx 2 + y = sin x dx + y = x cos x (4 2 dx + y = 2 e x cos x 3 ( (2 (3 (4 dx + 2 dx 6y = x, y(0 = 0, y (0 = 0 dx 2 2 dx = xe2x, y(0 = 0, y (0 = dx + y = sin x, 2 y(0 = 0, y (0 = 0 dx + y = 2 e x cos x, y(0 =, y (0 = 0