Вправи: 68

68. Виконайте дії:

1) xy-1 + 21-y = xy-1 + 2-(y-1) = xy-1 – 2y-1 = x-2y-1;

2) 3cc-d + 3dd-c = 3cc-d + 3d-(c-d) = 3cc-d – 3dc-d = 3c-3dc-d = 3(c-d)c-d = 3;

3) 3m+2n2m-3n – m-8n3n-2m = 3m+2n2m-3n – m-8n-(2m-3n) = 3m+2n2m-3n + m-8n2m-3n = 3m+2n+m-8n2m-3n = 4m-6n2m-3n = 2(2m-3n)2m-3n = 2;

4) b22b-14 + 4914-2b = b22b-14 + 49-(2b-14) = b22b-14 – 492b-14 = b2- 492b-14 = b-7(b+7)2(b-7) = b+72.