Вправи: 86

86. Спрости вираз.

а) 6a2+15ab-8ac-20bc12a2-9ab-16ac+12bc = 3a2a+5b-4c(2a+5b)3a4a-3b-4c(4a-3b) = (2a+5b)(3a-4c)(4a-3b)(3a-4c) = 2a+5b4a-3b.

б) 2a2-18a2+2a-15 = 2(a-3)(a+3)a2+2a+1-16 = 2(a-3)(a+3)(a+1)2-16 = 2(a-3)(a+3)(a+1+4)(a+1-4) = 2(a-3)(a+3)(a+5)(a-3) = 2(a+3)a+5;

в) x(y+1)2- y(x+1)2xy+1- y(x+1) = xy2+2xy+ x-yx2-2xy- yxy+ x- yx- y = -xyx- y+(x- y)x- y = (x-y)(1- xy)x- y = 1 – xy.