Question

Factor completely 4a^2 - 8a - 5

Answer 1

Answer:

Step-by-step explanation:

Use the quadratic formula first; find the roots, and then write the factors based upon the roots.  Here, a = 4, b = -8 and c = -5.  Thus, the discriminant b^2 - 4ac is (-8)^2 - 4(4)(-5), or 64 + 80, or 144.

Thus, we have:

      -(-8) ± √144            8 ± 12

x =  --------------------- = -------------- = 5/2 and x = -1/2

              2(4)                     8

If x = 5/2 is a root, then (2x - 5) is a factor.

If x = -1/2 is a root, then (2x + 1) is the other factor.

or