Question

Help me with this question please?

Answer 1

$\bf 3^{n+2}-3^n=8\cdot 3^n\implies \boxed{3^n\cdot 3^2}-3^n=8\cdot 3^n \\\\\\ \stackrel{common~factor}{3^n}(3^2-1)=8\cdot 3^n\implies 3^2-1=\cfrac{8\cdot \underline{3^n}}{\underline{3^n}}\implies 3^2-1=8 \\\\\\ 9-1=8\implies 8=8$