Відповіді на вправи: 8.27

8.27. Скоротіть дріб:

1) x2+ x-67x+21 = x-2(x+3)7(x+3) = x-27;

2) 2y-168+7y- y2 = 2(y-8)-y+1(y-8) = –2y+1;

y² – 7y – 8 = 0; y₁ = 8; y₂ = –1;

3) 3a2+ a-24- 9a2 = 3a- 23(a+1)2-3a2+3a = –2-3a(a+1)2-3a(2+3a) = –a+12+3a;

3a² + a – 2 = 0; D = 1² – 4 • 3 • (–2) = 1 + 24 = 25;

a₁ = -1+56 = 46 = 23; a₂ = -1-56 = –66 = –1.