Re: [理工] [工數] ODE 請神人看一下...櫃求
※ 引述《himanbobo (I have a dream)》之銘言:
: ※ 引述《topee (eason)》之銘言:
: : y
: : y'= 2x^2 + ----
: : x
: : y(1)=5
: : 誰能算出嗎??
: : 感謝你^^
: dy/dx = 2x^2 + y/x
: => xdy = 2x^3 dx + y dx
: => xdy-ydx = 2x^3 dx
: => (x^2)*d(y/x) = 2x^3 dx
: => d(y/x) = 2xdx
: => y/x = x^2 + c
: => y = x^3 + cx
: 代入Initial condition:
: 5 = 1 + c ===> c = 4
: 所以 y = x^3 + 4x
y
大大我題目打錯了 是y'=3x^2 + ---
x
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