What is the value of $-a-b^2+3ab$ if $a=-1$ and $b=5$?
I will start by replacing $a$ with $-1$ and $b$ with $5$ in the expression: $$-(-1)-(5)^2+3(-1)(5)$$ Next, I will simplify the parentheses and exponents: $$1-25-15$$ Finally, I will combine the like terms: $$1-25-15=-39$$ 