Question

(1-3x/x^2-1)=(M/x+1)+(N/x-1),求M,N的值

Answer 1

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