2x^4-3x^3+mx^2+7x+n
設(shè)分解后因式乘積(x+2)(x-1)(2x^2+ax+b)
=(x^2+x-2)(2x^2+ax+b)
=2x^4+(a+2)x^3+(a+b-4)x^2+(b-2a)x-2b
=2x^4-3x^3+mx^2+7x+n
每項(xiàng)對(duì)應(yīng)有
a+2=-3,a=-5
a+b-4=m
b-2a=7,b=7+2a=-3
-2b=n
-5-3-4=m=-12
n=-2b=6