-7x² - 15x - 8 = 0;
D = 15² - 4*7*8 = 225 - 224 = 1²;
x₁ = (15-1)/(-14) = -1;
x₂ = (15+1)/(-14) = -16/14 = -8/7;
-7x² - 15x - 8 = -7(x+1)(x+8/7).
-7x² - 15x - 8 = 0;
D = 15² - 4*7*8 = 225 - 224 = 1²;
x₁ = (15-1)/(-14) = -1;
x₂ = (15+1)/(-14) = -16/14 = -8/7;
-7x² - 15x - 8 = -7(x+1)(x+8/7).