Respuesta :

Inside of box is :

[tex]\begin{gathered} x\times x \\ 5\times x \\ 3\times x \\ 5\times3 \end{gathered}[/tex]

So the product is:

[tex]\begin{gathered} (x\times x)+(5\times x)+(3\times x)+(5\times3) \\ x^2+5x+3x+15 \\ x^2+8x+15 \end{gathered}[/tex]

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