Answer
$t^2+6t+9$
Work Step by Step
$x^m \cdot x^n = x^{m+n}$
Use the rule above to obtain:
$=(t+3)^{7+(-5)}
\\=(t+3)^{2}$
Use the formula $(a+b)^2=a^2+2ab+b^2$, where $a=t$ and $b=3$, to obtain:
$=t^2 + 2(t)(3) + 3^2
\\=t^2+6t+9$