Answer :
You have y in terms of x. Solve for x in terms of y.
y = 9x^2 - 4
Add 4 to both sides:
y + 4 = 9x^2
Divide both sides by 9:
(y+4)*(1/9) = x^2
Take the square root of both sides:
(y+4)^(1/2) * (1/9)^(1/2) = x
(y+4)^(1/2) * 1/3 = x
x = 1/3(y+4)^(1/2)
y = 9x^2 - 4
Add 4 to both sides:
y + 4 = 9x^2
Divide both sides by 9:
(y+4)*(1/9) = x^2
Take the square root of both sides:
(y+4)^(1/2) * (1/9)^(1/2) = x
(y+4)^(1/2) * 1/3 = x
x = 1/3(y+4)^(1/2)