Is function invertible

Question

Prove or disprove: If a, b and c are real numbers where 'a' is not equal to 0, then ax^2 + bx + c is invertible.

Answer 1

This is not true. For example take f(x)=x^{2}. This is not a 1-1 function which means that f is not invertible. For instance, f(1)=f(-1)=1.