若x^2+x-2與2x-1分別是ax^3+bx^2+cx-5及ax^3+bx^2+x-25/16的因式,求a+b+c.

若x^2+x-2與2x-1分別是ax^3+bx^2+cx-5及ax^3+bx^2+x-25/16的因式,求a+b+c.


設(x^2+x-2)*(mx+n)=ax^3+bx^2+cx-5,那麼就有a+b+c=2n,2n=5兩個關係,所以a+b+c=5



化簡ax^2-3ax=0


ax^2-3ax=0
ax(x-3)=0
當a=0時,解為全體實數
當a≠0時x1=0,x2=3



化簡:1x(x+1)+1(x+1)(x+2)+1(x+2)(x+3)+1(x+3)(x+4).


原式=1x-1x+1+1x+1-1x+2+1x+2-1x+3+1x+3-1x+4=1x-1x+4=4x(x+4).