You are heating liquid in a chemistry lab. Four minutes ago, the temperature of the liquid was - 4 degrees Celsius. Since then, it has been going up at a steady rate of 2 degrees per minute.

A. Write an equation that tells you the relationship between temperature and time at any given time. Designate the current time as 0.

B. Use your equation to predict the temperature of the liquid 15 minutes from now.

The rate of temperature rise is 2 degrees/minute.

The relation between temperature and time is of the form

y = 2x + b

where

x = time, minutes,

y = temperature, Celsius

When x = - 4 min, y = - 4°C because the temperature was - 4°C 4 minutes ago. Currently, x = 0.

Therefore

-4 = 2 (-4) + b

-4 = - 8 + b

4 = b

Part A

The relation is y = 2x + 4

Part B

When x = 15 (15 minutes from now), the temperature will be

y = 2 (15) + 4 = 34°C

Answer: 34°C