8. Add

(x2 + 7x - 8) + (2x2 - 4x + 5)

Remove parentheses and combine like terms.

x2 + 7x - 8 + 2x2 - 4x + 5

When we remove parentheses, we multiply the factor in front of the parentheses by all the terms inside the parentheses. If we don't see a factor in front of the parentheses, it is an invisible 1. The identity property says that multiplying by 1 leaves everything the way it was. The conclusion to be drawn here is that if there is nothing in front of the parentheses, nothing happens when we remove them. Now combine like terms

3x2 + 3x - 3

There is another popular format for these addition of polynomial problems. Since we are going to combine like terms, it would be helpful if we lined up the like terms in a vertical format.