express the function by a formula and draw the graph indicating that portion of the graph which has a meaning in the problem.
1. the amount of 1 dollar at 4% simple interest, as a function of time.
The formula for the future amount F of an investment P at a simple interest r is;
$$F = P(1 + rt)$$
where t is the time in year. If you plot this expression into a graph of F versus t, you will get a straight line with (0, P) as an F-intercept. The portion of a graph that has a meaning is when t ≥ 0.
In your problem, just replace P by $1 and r by 0.04.