(x+3)^2 <--- ???

(X+3)^2$${{\mathtt{X}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{6}}{\mathtt{\,\times\,}}{\mathtt{X}}{\mathtt{\,\small\textbf+\,}}{\mathtt{9}}$$

it is true. we can write it anyway.

(x + 3)² = (x + 3)(x + 3)

Using FOIL:  First, Outside, Inside, Last:

(x + 3)(x + 3)  =  x·x  +  x·3  +  3·x  +  3·3  =  x²  +  3x  +  3x  +  9  =    x²  +  6x  +  9