Question

Solving quadratic equation using the completing the square method. (a).x²+20x-12=0​

Answer 1

Answer:

$x = -10 + 4 \sqrt7 \ , \ x = -10 - 4 \sqrt7$

Step-by-step explanation:

x²+20x-12=0

a = 1, b = 20, c = -12

$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2x}$

$x = \frac{-20 \pm \sqrt{448}}{2}\\\\x = \frac{-20 \pm \sqrt{8 \times 8 \times 7}}{2}\\\\x = \frac{-20 + 8\sqrt{7}}{2} \ , \ x = \frac{-20 - 8 \sqrt7}{2}\\\\x = \frac{-10 + 4\sqrt{7}}{1} \ , \ x = \frac{-10 - 4 \sqrt7}{1}\\\\x = -10 + 4 \sqrt7 \ , \ x = -10 - 4 \sqrt7$

Answer 2

Answer:

Step-by-step explanation:

x² + 20x - 12 = 0

x² + 20x +     = 12

now add the square of half the "b" value to each side

x² + 20x + 100 = 12 + 100

(x + 10)² = 112

x + 10 = ±√112

x = -10 ± √112

x = -10 ± 4√7