Question

.......................

Answer 1

$tt cfrac{a^2-81}{2a^2-18a}= cfrac{(a-9)(a+9)}{2a(a-9)}=cfrac{a+9}{2a}\\ npu a=-0.1\\ cfrac{a+9}{2a}=cfrac{-0.1+9}{2(-0.1)}=cfrac{8.9}{-0.2}=-cfrac{89}{2}=-44.5$