= 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。