124.
а) \(\dfrac{y^2-16}{10xy}\cdot\dfrac{5y}{3y+12}=\dfrac{y-4}{6x}\)
б) \(\dfrac{b-a}{a}\cdot\dfrac{3ab}{a^2-b^2}=-\dfrac{3b}{a+b}\)
125.
а) \(\dfrac{a^2-1}{a-b}\cdot\dfrac{7a-7b}{a^2+a}=\dfrac{7(a-1)}{a}\)
б) \(\dfrac{b^2+2bc}{b+3}\cdot\dfrac{5b+15}{b^2-4c^2}=\dfrac{5b}{b-2c}\)
в) \(\dfrac{(x+3)^2}{2x-4}\cdot\dfrac{x^2-4}{3x+9}=\dfrac{(x+3)(x+2)}{6}\)
г) \(\dfrac{(5-y)^2}{2y+12}\cdot\dfrac{y^2-36}{2y-10}=\dfrac{(y-5)(y-6)}{4}\)
