4. Suppose that you after 3 months you have $350 in yor account and after 7 months you have $650.

- a) Let
*x*denote the number of months the and let*y*denote the amount of money in the account. Find a linear equation which will predict how much money you will have in the account as a function of the number of months - b) Graph this function.
- c) Use this function to determine how much money you will have after 12 months.

a) If we let *x* denote the number of months the
and let *y* denote the amount of money in the account, then

and

To find a linear equation, first find the slope.

Next, use the point-slope form of the equation

*y* - *y*_{1} = *m*(*x* - *x*_{1 })

Plug in our numbers.

To solve for *y*, remove parentheses,

and add 350 to both sides

This would tell you how much money you would have in your account if you opened the account with $125 and put in $75 each month (and there was no interest accumulating).

c) To compute the amount after 12 months, we plug in a 12 for the
*x* in the equation.