Question

If 4x^2 – bx + 81 is a perfect square trinomial. Then the value of b is

Answer 1

b = 36

Explanation:

perfect square: a² - 2ac + c²

4x²- bx + 81 = (2x)² - bx + 9² = (2x)² - 2*(2x)*(9) +9²= (2x)² - 36x +9²,

so b = 36