Alice invests $5000 in two certificates of deposit; the interest on the first certificate is 4%, and the interest on the second is 5%. Let's denote the amount she invests in the first certificate by x. Then the amount she invests in the second certificate is
.
The interest she receives on the first certificate is
,
and the interest she receives on the second certificate is
.
So a function that models the total interest she receives from both certificates is
y =
.