at first year 5000 compact discs were sold.
and it increased at a rate of 15000 per year in the upcoming year .
we need to linear function which mean if we graph it will get a straight line.
which is in the form of y=mx+b
where y=f(t) which means functions represented in time.
where 15000 is the slope of the equation which is increasing at this rate.
and b is the y intercept which mean from 5000 sales has been increased.
so the linear equation is
