Chapter P, Prerequisites - Section P.6 - Factoring - P.6 Exercises - Page 42: 28

$(a-6b)(a+6b)$

The given expression can be written as: $=a^2-6^2b^2 \\=a^2-(6b)^2$ RECALL: $A^2-B^2=(A-B)(A+B)$ Factor the difference of two squares using the formula above with $A=a$ and $B=6b$ to obtain: $=(a-6b)(a+6b)$