Evaluate $3x^2+5x-1$ if $x=7$.
I want to find the value of the expression when x is 7, so I will substitute 7 for x in the expression and simplify. I can use parentheses to help me keep track of the substitution: $3(7)^2+5(7)-1$. Next, I will follow the order of operations and evaluate the exponents first: $3(49)+5(7)-1$. Then, I will multiply: $147+35-1$. Finally, I will add and subtract from left to right: $182-1=181$. 