Question

For the function f(x) = 2 – 3x, find f(4). A. 12 B. –5 C. –10 D. 14

Which relation is a function? A. {(1, 2); (2, 3); (3, 4); (1, 5)} B. {(1, 2); (2, 3); (3, 4); (2, 5)} C. {(1, 2); (2, 5); (3, 2); (4, 5)} D. {(1, 2); (1, 3); (3, 2); (4, 2)}
Please explain how would you solve these problems do not just give me the answer i want to know how to do it for the next time i have issues.