Answer:
C.7, -2
Explanation:
A quadratic equation is a polynomial of degree two. A quadratic equation is in the form:
ax² + bx + c = 0; where a, b, c are constants.
Quadratic equation can be solved using different methods, such as completing the square method, quadratic formula.
Solving the equation 2x² - 10x - 20 = 8 using completing the square:
2x² - 10x - 20 = 8
2x² - 10x = 28
Divide through by 2, to make the coefficient of x² to be 1:
x² - 5x = 14
Add to both sides, the square of half of the coefficient of x [i.e. (-5/2)² = 6.25]
x² - 5x + 6.25 = 14 + 6.25
(x - 2.5)² = 20.25
taking square root of both sides:
x - 2.5 = √20.25
x - 2.5 = ±4.5
x = 2.5 ± 4.5
x = 2.5 + 4.5; or x = 2.5 - 4.5
x = 7 or x = -2