X² + 16x = - 63
x² + 16x + 63 = 0
D = 16² - 4*1*63 = 256 - 252 = 4 =2²
D>0
x₁ = ( - 16 - 2)/(2*1) = - 18/2 = - 9
x₂ = ( - 16 + 2)/(2*1) = -14/2 = - 7
Проверим:
(-9)² + 16 * (-9) = 81 - 144 = -63
(-7)² + 16 * (-7) = 49 - 112 = - 63
Ответ : х₁ = - 9 ; х₂ = - 7 .
1)2х-5-6х=11
-4х-5=11
-4х=11+5
-4х=16
х=-4
2) -5х+7=13
-5х=13-7
-5х=6
х=-6/5
х=-1 1/5
х=-1.2