I need to solve this equation by completing the square:

2x^2 + x - 8 = 0

In my textbook the answer is x = 1.77 or x = -2.27

I've tried to do it but can't get the right answer...

2x^2 + x - 8 = 0

x^2 + 0.5x - 4 = 0

x^2 + 0.5x = 4

x^2 + 0.5x + 0.0625 = 4.0625

(x + 0.0625)^2 = 4.0625

x + 0.0625 = (+/-)sqrt4.0625

x = - 0.0625 + sqrt4.0625 or x = - 00625 - sqrt4.0625

x = 1.95... or x = -2.07...

Thanks.