Задание по алгебре

122) (x/y - y/x) : (1/x + 1/y) =
= (x^2 - y^2)/xy : (y+x)/xy =
= (x+y)(x-y)/xy * xy/(x+y) =
= (x+y)/(x+y) * (x-y) * xy/xy =
= 1 * (x-y) * 1 = (x - y)


124) = (a^2 - b^2)/ab : (a+b)/3ab =
= (a+b)(a-b)/ab * 3ab/(a+b) = 3*(a-b)

126) = (x^2 - y^2)/y : (x+y)/y =
= (x+y)(x-y)/y * y/(x+y) = (x-y)

128) = ((3a+1) - (2a+2))/(2a+2) : (6a-6)/(a+1) =
= (a-1)/2*(a+1) * (a+1)/6*(a-1) =
= (a-1)/(a-1) * (a+1)/(a+1) * 1/2 * 1/6 = 1/12