Answer
$$9x^2-30x+25$$
Work Step by Step
We normally multiply these expressions out using the distributive property, ensuring that every value multiplied by a given set of parenthesis is multiplied by everything inside of the parenthesis. However, in this problem, we use the fact that the binomial is squared as a shortcut to obtain:
$$ \left(3x-5\right)^2\\ \left(3x\right)^2-2\cdot \:3x\cdot \:5+5^2\\ 9x^2-30x+25$$
