Answer
$3ab+4$
Work Step by Step
Divide $4a^4b$ to each term of the numerator to have:
$\require{cancel}
\\=\dfrac{12a^5b^2}{4a^4b} + \dfrac{16a^4b}{4a^4b}
\\=\dfrac{\cancel{12a^5b^2}3ab}{\cancel{4a^4b}} + \dfrac{\cancel{16a^4b}4}{\cancel{4a^4b}}
\\=3ab+4$
