Question

Find the value for c, that would make x^2-12x+c, a perfect square

Answer 1

 Complete the square to find the value of this constant: 
4x² + 12x + c = (2x + 3)² 
4x² + 12x + c = 4x² + 12x + 9 
By comparing coefficients, it is easy to see that c = 9.