Mustafa was asked whether the following equation is an identity: x(9x+3)+3(x+3)=9(x+1)^2x(9x+3)+3(x+ 3)=9(x+1)
2
x, left parenthesis, 9, x, plus, 3, right parenthesis, plus, 3, left parenthesis, x, plus, 3, right parenthesis, equals, 9, left parenthesis, x, plus, 1, right parenthesis, squared
He performed the following steps:
\begin{aligned} &\phantom{=}x(9x+3)+3(x+3) \xhookrightarrow{\text{Step }1}\quad&=9x^2+6x+9 \xhookrightarrow{\text{Step }2}\quad&=(3x+3)^2 \xhookrightarrow{\text{Step }3}\quad&=(3(x+1))^2 \xhookrightarrow{\text{Step }4}\quad&=9(x+1)^2 \end{aligned}
Step 1


Step 2


Step 3


Step 4




=x(9x+3)+3(x+3)
=9x
2
+6x+9
=(3x+3)
2

=(3(x+1))
2

=9(x+1)
2



For this reason, Mustafa stated that the equation is a true identity.
Is Mustafa correct? If not, in which step did he make a mistake?