## Algebra 1

$I$
Given: $\dfrac{x^2-81}{2x^2+23x+45}$ As we know $(a^2-b^2)=(a-b)(a+b)$ Thus, $\dfrac{x^2-81}{2x^2+23x+45}=\dfrac{(x-9)(x+9)}{2x^2+18x+5x+45}$ $=\dfrac{(x-9)(x+9)}{(2x+5)(x+9)}$ $=\dfrac{(x-9)}{(2x+5)}$ Hence, the correct answer is $I$.