Solve for y. x-4=y^2

X - 4 = y^2

Since you want y to the first power you have to take the square root of y^2.

If you take the square root of the right side you also must take the square root of the left side.

+ - sqrt (x-4) = y

y = sqrt (x - 4)

and y = - sqrt (x - 4)