Im lost i don't know how to do this can someone show me step by step how to solve this

Question

For what value does c does the equation have one real root? Hint using the values of a and b found in the equation, solve D = 0 for c.

Consider the quadratic expression X^2 + 4x + c = 0.

Answer 1

There is no a, b or D shown in the equation.

x^2 + 4x + 4 = (x+2)^2