If the roots of equation x2-bxax-c=m-1m+1 are equal but opposite in sign, then the value of m will be

Given equation can be written as(m+1)x2-{m(a+b)-(a-b)}x+c{m-1}=0.Roots are equal and of opposite sign. So sum of roots is equal to zero.⇒0=m(x+b)-(a-b)⇒m=a-ba+b