need help with this completing the square problem

Question

w^2-w-20=0

 

I've done the problem already buti don't thing i did it right. i need help

Answer 1

it's easier to just factor: (w-5)(w+4)=0, but if you have to complete the square...

w^2-w-20=0

w^2-w=20

take half of -1 and square it (-1/2)^2=1/4=0.25

add 0.25 to both sides of the equation

w^2-w+0.25=20+0.25

(w-0.5)^2=20.25

take the square root of both sides

+(w-0.5)=4.5

w-0.5=4.5

w=5

-w+0.5=4.5

-w=4.5-0.5

-w=4

w=-4