A young sumo wrestler decided to go on a special high protein diet to gain weight rapidly. He started at 90 kilograms and gained weight at a constant rate. After 8 months he weighed 138 kilograms. What is the functions formula

Since this is linear, has a constant velocity, "slope", or rate, it can be expressed as:

y=mx+b, where m = (y2-y1) / (x2-x1) and b=initial value or y-intercept.

m = (138-90) / (8-0)

m=6, and we know the initial mass (mass is in kilograms, weight or force is in Newtons : P) was 90 so:

y=6x+90