Question

If (x − 3) (x – 7) = x
2 − ax + 21, then the value of a = _________.

Answer 1

Step-by-step explanation:

If (x-3) and (x+7) are factors, then we can multiply them. That gives

x^2 +4x - 21.

My guess is that you mistyped the problem, and you meant x^2 + ax - 21. In that case, a = 4.