147. Разложите на множители трёхчлен, выделив квадрат в двучлена: 1) x² + 2x - 8; 2) x² - 6x + 5; 3) x² + 12x + 11; 4) x² - 4x - 5.

1) $x^2 + 2x - 8 = (x^2 + 2x + 1) - 9 = (x + 1)^2 - 3^2 = (x + 1 - 3)(x + 1 + 3) = (x - 2)(x + 4)$ 2) $x^2 - 6x + 5 = (x^2 - 6x + 9) - 4 = (x - 3)^2 - 2^2 = (x - 3 - 2)(x - 3 + 2) = (x - 5)(x - 1)$ 3) $x^2 + 12x + 11 = (x^2 + 12x + 36) - 25 = (x + 6)^2 - 5^2 = (x + 6 - 5)(x + 6 + 5) = (x + 1)(x + 11)$ 4) $x^2 - 4x - 5 = (x^2 - 4x + 4) - 9 = (x - 2)^2 - 3^2 = (x - 2 - 3)(x - 2 + 3) = (x - 5)(x + 1)$