Question

(x-2)(xx+mx+n)=xxx+3xx-7x-6,求m与n的值

Answer 1

(x-2)(xx+mx+n)=xxx+3xx-7x-6

(x-2)(xx+mx+n) 展开

=x³+mx²+nx-2x²-2mx-2n

=x³+(m-2)x²+(n-2m)x-2n

因为有x³+(m-2)x²+(n-2m)x-2n=x³+3x²-7x-6

所以m-2=3 m=5

-2n=-6 n=3