Can you solve these equation by completing the square

2x^2+7x-4=0
3x^2x-1=0

1 answer

I'll do one, and you try the other.

2x^2+7x = 4
(x^2 + 7/2 x) = 2
(x^2 + 7/2 x + (7/4)^2) = 2 + (7/4)^2
(x + 7/4)^2 = 81/16
x + 7/4 = ±9/4
x = -7/4 ± 9/4
x = -4 or 1/2

Just recall that (x+a)^2 = x^2 + 2ax + a^2

That's why I added (7/4)^2 to both sides.

The second one has a typo, so fix it and follow the same logic.