Question

若m/(x+4)-n/(x-4)=6x/(x^2-16),求mn的值

Answer 1

m/(x+4)-n/(x-4)

=[m(x-4)-n(x+4)]/(x^2-16)

=[(m-n)x-4(m+n)]/(x^2-16)

m-n=6 m+n=0

解得：

m=3 n=-3

mn=3×（-3）=-9