Aline that has a y-intercept of 0 and passes through (12, 4)

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

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.