We are given product demand, the time-series trend equation is 53 – 4x.
Where, x represents the time over the demand.
We know, slope-intercept of a linear equation
y=mx+b, where m is the slope (some time we call it rate of increase or decrease) and b is y-intercept (fix value).
Let us write given expression in slope-intercept form.
In order to write it in slope-intercept form we need to write x term first.
So, 53 – 4x could be written as -4x+53.
Here, we have negative sign in front of 4.
That represents, change in demand and because it is a negative number so we could say, demand is getting decrease at the rate 4 over the unit time.