= (Mx + my + nx + my) / (mx - my + nx - ny)= (M(x + y) + n(x + y)) / (m(x - y) + n(x - y))= ((x + y)(M + n)) / ((x - y)(m + n))
= (Mx + my + nx + my) / (mx - my + nx - ny)
= (M(x + y) + n(x + y)) / (m(x - y) + n(x - y))
= ((x + y)(M + n)) / ((x - y)(m + n))