The perfect square of 4a^2 - 9a + 5 = 0

Question

The method that I use is the formula of -b± √b² − 4(a)(c) / 2(a)

And the answer that I get are: 5/9 and 4/9, however, In my worksheet, It says that the answers are 5/4 and 1.

I want to know what I'm doing wrong please

Answer 1

The quadratic formula gives [9±sqrt(81-80)]/8 = (9±1)/8 = 1 and 5/4.

However, it sounds as if the problem wants you to do this by completing the square which goes like this

4a² - 9a + 5 = [2a - (9/4)]² - 81/16 + 5 =0

2a - (9/4) = ±1/4

8a = 9±1

as before!