Question

Solve by completing the square​

Answer 1

Answer:

Your answers would be:

x = 10 and x = -8

Step-by-step explanation:

Solve for the zeros:

x² - 2x - 78 = 2

Subtract both sides by 2.

x² - 2x - 80 = 0

Use the quadratic formula: $x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$

a = 1

b = -2

c = -80

Plug in and solve:

$x=\frac{-(-2)\pm\sqrt{(-2)^2-4(1)(-80)}}{2(1)}\\\\x=\frac{2\pm\sqrt{(-2)^2-4(1)(-80)}}{2(1)}\\\\x=\frac{2\pm\sqrt{4-4(-80)}}{2(1)}\\\\x=\frac{2\pm\sqrt{4+320}}{2(1)}\\\\x=\frac{2\pm\sqrt{324}}{2(1)}\\\\x=\frac{2\pm18}{2}$

Solve for +:

$x=\frac{2+18}{2}\\\\x=\frac{20}{2}\\\\x=10$

Solve for -:

$x=\frac{2-18}{2}\\\\x=\frac{-16}{2}\\\\x=-8$