Question

A mother gives birth to a 7-pound baby. Every 3 months, the baby gains 2 pounds. If x is the age of the baby in months, then y is the weight of the baby in pounds. Find an equation of a line in the form y=mx+b that describes the baby's weight.

y =___________________

Answer 1

y = 2/3 x + 7

Explanation:

At birth represents the beginning of time for the baby. Lets call this month zero. So here are your coordinates.

x = 0 y = 7 ----> at birth

x = 3 y = 9

x = 6 y = 11

x = 9 y = 13

Now we find the slope between each point. Since the common difference of y is 2 and the common difference in x is 3 , the slope will be

slope = y / x = 2 / 3

Therefore, the equation of the line that represents this relationship is

y = (2/3) x + 7