Answer:
x^2+6x+9= (x+3)^2
Step-by-step explanation:
x^ 2 +6x+__ =(_)^ 2
The formula is a^2+2ab+b^2= (a+b)^2
x^2= a^2
x=a
6x=2ab where a=x
6x=2x*b
b=3
b^2=9
