Question:

# Simplify: $$\left(\right.7y^{2}+3xy-9\left.\right)-\left(\right.2y^{2}+3xy-5\left.\right)$$

A $$5y^{2}-4$$
Explaination

When subtracting polynomials the first step is to distribute the negative sign through the parentheses. This changes the sign on each term inside the parentheses: $$7y^{2}+3xy-9-2y^{2}-3xy+5$$ Arrange like terms next to each other (optional): $$7y^{2}-2y^{2}+3xy-3xy-9+5$$ Combine like terms to compute the answer: $$5y^{2}-4$$