How do you solve by completing the square: 2x^2 - 7x -15 = 0?

1 Answer
Jim G.
Jun 8, 2018

x=-3/2" or "x=5

Explanation:

"to solve by "color(blue)"completing the square"

"add 15 to both sides"

2x^2-7x=15

"the coefficient of the "x^2" term must be 1"

"divide all terms by 2"

x^2-7/2x=15/2

"add "(1/2"coefficient of x-term")^2" to both sides"

x^2+2(-7/4)x color(red)(+49/16)=15/2color(red)(+49/16)

(x-7/4)^2=169/16

color(blue)"take the square root of both sides"

x-7/4=+-13/4

x=7/4+-13/4

x=7/4-13/4=-3/2

"or "x=7/4+13/4=5

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