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

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

x1 = 3, y1 = 350

and

x2 = 7, y2 = 650

To find a linear equation, first find the slope.

= $75/mo

Next, use the point-slope form of the equation

y - y1 = m(x - x1 )

y - 350 = 75(x - 3)

To solve for y, remove parentheses,

y - 350 = 75x - 225

and add 350 to both sides

y = 75x - 225 + 350

y = 75x + 125

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).

b) The graph would look like

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

y = 75(12) + 125

= 900 + 125

= 1025

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