1) a(b^2 - c^2) 3(a+4) (b-c)(b+c) * 3
----------------- * ----------- = -------------------- = 1,5(b-c)
2(a+4) a(b+c) 2(b+c)
2) (2x - 5y)(2x + 5y) (x^2 - 2x = 4) 2x - 5y
--------------------------- * ------------------- = ------------
(x + 2)(x^2 - 2x + 4) (2x + 5y) x + 2