Solve the quadratic function y=2x^2-14x -16 by completing the square. Round roots to the nearest hundredth, if necessary. Show your work.

2 answers

Look for two factors for each of the two end terms.

16 = 4,4 or 8,2 or 16,1

2 = only 2,1

By combining them, what will add to -14?

Remember that one has to be negative.

That is the beginning of your work. Carry on.
2x^2-14x -16 = 0
(x^2-7x) = 8
(x^2-7x+(7/2)^2) = 8 + (7/2)^2
(x - 7/2)^2 = 32/4 + 49/4
(x - 7/2)^2 = 81/4
x - 7/2 = ±9/2
x = 7/2 ± 9/2
x = -1,8