Question

mario invests $1,500 in a savings account that earns 2% interest a year. he also plans to set aside $50 cash a month.
$x = \text{number of years}$
savings account: $f(x) = 1500(1.02)^x$
cash savings: $g(x) = 50(12x)$
which function represents the total amount mario will save over $x$ years?
$2100(1.02)^x$
$1500(1.02)^x + 600x$
$500(1.02)^x - 600x$
$2100x$

Explanation:

Step1: Simplify cash savings function

Simplify $g(x)=50(12x)$:
$g(x)=50\times12x=600x$

Step2: Sum the two savings functions

Total savings = savings account + cash savings:
$Total(x)=f(x)+g(x)=1500(1.02)^x + 600x$

Answer:

1500(1.02)$^x$ + 600x