Question

After 3 minutes, a submarine had descended to −550 feet. After 8 minutes, the submarine had descended to −600 feet. Assuming a linear function, write an equation in the form d(t)=mt+b that shows the depth, d(t), after t minutes.

Answer 1

d(t)=-10t-520

Explanation:

First you have to find the gradient (m) using the formula
`m=(d(t)2-d(t)1)/(t2-t1)`

using the two points you have been given: 1(3,-550) and 2(8,-600)

so you substitute these points into the equation
`m=(-600+500)/(8-3)`

m=-10

Now that you have found the m-value you need to find the b-value by using one of the points you already have, I will use Point 2 (8,-600), and substitute it into the equation and solve

d(t)=-10t+b

-600=-10*8+b

-600=-80+b

-520=b

Therefore, the equation is d(t)=-10t-520