= m(x- 1)+n(x-2)/(x- 1)(x-2)

=(m+n)x-m-2n/(x- 1)(x-2)，

Known by

(m+n)X-m-2n/(X- 1)(X-2)=(X-8)/(X+ 1)(X-2)，

Then (m+n)x-m-2n=X-8, so m+n= 1, -m-2n=-8.

The solution is m=-6 and n=7.

2. From (1/a)+(1/b) =1/(a+b), we get.

B(a+b)+a(a+b)=ab, then A? +b？ =-ab，

b/a+a/b=(a？ +b？ )/(ab)=-ab/(ab)=- 1。