Question

Over three years ago Lucius a $550 $600 and $650 from Babysitting the polynomial 550 X to the 3rd+600 X squared +650 X represents her savings with interest after three years the annual interest rate equals X minus one find the interest needed so that she will have $200 after three years

Answer 1

about 5.52%

Explanation:

If Lucius wants an account value of $2000 after 3 years, she can find the interest rate by solving the polynomial ...

550x³ +600x² +650x -2000 = 0

This equation has one positive real root. It is irrational, so must be found using the rather complicated cubic solution formula or, more simply, a graphing calculator. The latter shows the root to be near 1.05516.

Lucius needs an interest rate of ...

(1.05516 -1)×100% = 5.516%

The interest rate needed for a balance of $2000 after 3 years is about 5.52%.