如題...
誰能把整個運算過澄清清楚的寫出來.....
千萬不要跳過程
不然看不懂 Orz.............................
題目： y"' + y" = (e^x)cosx
講義解的= =
( D^3 + D^2 ) y =(e^x)cosx
移項成逆運算公式：
Yp = [1/ ( D^3 + D^2 )] ( e^x ) cosx
= [ 1/(D+1)^3 + (D+1)^2 ] ( e^x ) cosx ---------->為何會變這樣Orz...
整理
Yp = e^x [ 1 / ( D^3 + 4D^2 + 5D + 2 ) ] cosx
= e^x [ 1 / ( 4D - 2 ) ] cosx..........................看不懂又跳太快
= e^x [ ( 4D + 2 ) / ( 4D - 2 ) ( 4D + 2 ) ] cosx
= e^x [ ( 4D + 2 ) / ( 16D - 4 ) ] cosx
= e^x [ ( 4D + 2 ) / 20 ] cosx.........................又看不懂了\ = =投降
= e^x [ ( 1 / 5 ) sinx - ( 1 / 10 ) cosx ]....................天阿根本是天書跳太快了
它的特解根本看不懂跳太快................
誰能幫我算沒跳過的全解......Orz....拜託了
