Question

(xx+mx+n)(x-3x+4)不含x的三次方与二次方求m,n的值

Answer 1

(x²+mx+n)(x²-3x+4)
=x^4+(m-3)x³+(4-3m+n)x²+(4m-3n)x+4n
不含则系数为0
m-3=0,4-3m+n=0
m=3
n=3m--4=5

Answer 2

右边通分
=[m(x-1)+n(x+1)]/(x+1)(x-1)
=[(m+n)x+(n-m)]/(x+1)(x-1)
=(-3x+1)/(x+1)(x-1)
所以(m+n)x+(n-m)=-3x+1
所以m+n=-3
n-m=1
相加
2n=-2
n=-1
m=n-1=-2