The expression obtained in the previous step can be now as the .
x2+bx+(2b)2=(x+2b)2
This will be applied to the expression
x2+6x+9.
x2+6x+9
x2+2⋅3x+9
x2+2x⋅3+9
(x+3)2
Therefore, a perfect square trinomial is obtained by adding a constant
c=(2b)2 to the initial expression in the form
x2+bx.