Given the expression x^2 + 8x + c, for us to get the constant c that will make it a perfect square we will use the completing the square method.
The constant can be gotten by taking the square of the half of coefficient of x in the equation.
The half of 8 will give us 8/2 = 4
Then we will square the resulting value 4.
4^2 = 16
Hence the value of c that will make it a perfect square is 16