Question

Which method would you NOT use on x^2-8x=9

A. Factoring
B. Square root
C. Completing The Square
D. Quadratic Formula

Answer 1

B

Explanation:

All of the choices are ways to solve x^2 - 8x = 9 except for square rooting.

A. We can factor x^2 - 8x = 9 by first making it into x^2 -8x - 9 = 0 and then factoring into: (x - 9)(x + 1) = 0.

C. We can also complete the square by adding 16 to both sides:

x^2 - 8x + 16 = 9 + 16 = 25 and then square rooting both sides from there.

D. We can finally use the quadratic formula (x =
`(-b+√(b^2-4ac) )/(2a)` or x =
`(-b-√(b^2-4ac) )/(2a)` ) to solve.

However, B will not work because you cannot easily square root (x^2 - 8x), if at all.

Thus, the answer is B.

Hope this helps!