I need the answer to number 9. Please! And if you have answers to the other questions;sharing them would be greatly appreciated. :D

This is so harddd! solve. 1 + 1 = solve 4 + 4 = solve 3 x 3

Select a graph that have an equation with a < 0

The function a represents the cost of manufacturing product a, in hundreds of dollars, and the function b represents the cost of manufacturing product b, in hundreds of dollars. a(t) = 5t + 2 b(t) = 7t - 2t +4 find the expression that describes the total cost of manufacturing both products, a(t) + b(t). a. 7t^2 - 7t + 2 b. 7t^2 + 3 +6 c. 7t^2 + 7t - 6 d. 7t^2 - 3t + 6