Question

A bathtub is draining at a constant rate. After 2 minutes, it holds 35 gallons of water. Four minutes later, it holds 15 gallons of water. Write an equation that represents the number y of gallons of water in the tub after x minutes

Answer 1

First find the rate or slope...

(y2-y1)/(x2-x1)=(15-35)/(4-2)=-20/2=-10

so far we have:

y=-10x+b, now we can use either point to solve for b, the y-intecept (initial amount)  I'll use (4,15)

15=-10(4)+b

15=-40+b

b=55

so the equation for the bathtub is:

y=-10x+55