For what value of c will this function have one zero? f(x) = X^2 +c
x² + c is actually a quadratic function. And x² + c = 0, it usually has two zeros which are solutions. But for when c = 0, x² + c = 0 x² + 0 = 0 x² = 0 Taking the square root of both sides. x = 0. Here it only has one zero. So the function x² + c, only has one root for c = 0.