Then, x = 3 . Explanation: I assume you mean to find the solution/root (radical) x , when f ( x ) = 0 . Then, this is simple. Just set f ( x ) to 0 and solve the equation for x : f ( x ) = 4 x − 12 = 0 First we can add 12 on both sides of the equality: 4 x − 12 + 12 = 0 + 12
which becomes 4 x = 12 We can now divide both sides of the equality by 4: 4 x 4 = 12 4
and we have x = 3 The "zero", or the solution for f ( x ) = 0 is x = 3 . Q.E.D.