I agree the answer is 225 and you can also use the calculator too.
To find the discriminant we use b^2 - 4ac
equation of 4x^2 - 3x + 3 = 0
a b c
-3^2 - 4 (4)(3) = -39
if b^2 - 4ac < 0, there are 2 complex roots or...no real roots...in this case imaginary.