Answer:
The expression for her balance is "B(t) = -75*t + 1500". It'll take her 20 months to pay off the loan.
Step-by-step explanation:
We are looking for a function that has the following points:
B(0) = 1500
B(4) = 1200
B(7) = 975
Between B(4) and B(7), there was a variation of 3 months and a variation of -225 on her balance, thefore for each month that passed there was a variation of -75. Thefore, the expression for her ballance is:
B(t) = -75*t + 1500
To check if this expression is valid, we will apply the values provided on the problem:
B(0) = -75*0 + 1500 = 1500 (valid)
B(4) = -75*4 + 1500 = -300 + 1500 = 1200 (valid)
B(7) = -75*7 + 1500 = -525 + 1500 = 975 (valid)
When she pays of her loan, B(t) = 0, so we need to solve for t as shown below:
B(t) = -75*t + 1500 = 0
-75*t + 1500 = 0
75*t = 1500
t = 1500 / 75 = 20 months
It'll take her 20 months to pay the loan.
