PLZZZ help me I don't get it?

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

Give the functions f(x) = |x + 2| - 3, what is the domain? a, b,c, or d all real numbers x > 2 x < -2 all real numbers and x cannot equal to 2

If a is a nonzero real number then the reciprocal of a is