Problema Solution

A quanity of y is initially -77 and decreases at a rate of 21 per day.

Find an equation y=mx+b that models the quanity y after x units of time.

Answer provided by our tutors

Since initially it is  = -77

hence   b = -77

change = 21 per day i.e    = -21 = m = slope

Hence equation

 y = -21x -77 this is the required equation in the for y = mx+b