The amount of money she will have after t years will be:
Given that:
A fund rate: 4.6% = 0.046
Saving account rate: 1.8% = 0.018
Let x is the amount Jacy invest in the fund so (1000-x) is the amount he invests in the savings account​
So a polynomial function S(x) to represent the interest Jacy will earn in 1 year is:
S(x) = 0.046x + 0.018(1000-x)
so we can simplify it as:
S(x) = 0.028+18