If a (x) = 3x + 1 and b (x) = square root of x-4, what is the domain of (b*a) (x) ?

A. (-infinity,+infinity)

B. (0, + infinity)

C. (1, + infinity)

D. (4, + infinity)

B. (0, + infinity)

When it is asked to know (b*a) (x), it is being asked to know what are the Y coordinates that are common in both graphs. When it a multiplication think of "and" - what are the Y that are on one graph and simultaneously on the other graph.

Design the graph of both functions on a calculator, or online, wherever. Then, look for when both functions have coordinates. All of them that are common to both graphs are the domain of (b*a) (x).