When Jordan moved into a new house, he planted two trees in his backyard. At the time of planting, Tree A was 36 inches tall and Tree B was 12 inches tall. Each year thereafter, Tree A grew by 2 inches per year and Tree B grew by 6 inches per year. Let AA represent the height of Tree A tt years after being planted and let BB represent the height of Tree B tt years after being planted. Graph each function and determine the number of years after the trees were planted when both trees have an equal height.

1 answer

To model the heights of the trees over time, we can create equations based on the growth patterns described.

Let \( t \) represent the number of years after planting.

For Tree A:

  • Initial height: 36 inches
  • Growth rate: 2 inches per year

The height \( A(t) \) of Tree A after \( t \) years is given by: \[ A(t) = 36 + 2t \]

For Tree B:

  • Initial height: 12 inches
  • Growth rate: 6 inches per year

The height \( B(t) \) of Tree B after \( t \) years is given by: \[ B(t) = 12 + 6t \]

Next, we want to find out when both trees have the same height. To do this, we set the two height equations equal to each other: \[ 36 + 2t = 12 + 6t \]

Now, let's solve for \( t \):

  1. Rearranging gives: \[ 36 - 12 = 6t - 2t \] \[ 24 = 4t \]
  2. Dividing both sides by 4: \[ t = 6 \]

Thus, both trees will be the same height after 6 years.

Calculating the height of both trees at \( t = 6 \):

  • For Tree A: \[ A(6) = 36 + 2 \cdot 6 = 36 + 12 = 48 , \text{inches} \]

  • For Tree B: \[ B(6) = 12 + 6 \cdot 6 = 12 + 36 = 48 , \text{inches} \]

Both trees will be 48 inches tall after 6 years.

Summary:

  • The trees will be the same height \( 6 \) years after being planted.
  • At that time, both will be \( 48 \) inches tall.

To graph the functions \( A(t) \) and \( B(t) \):

  1. Graph \( A(t) = 36 + 2t \):
    Starts at \( (0, 36) \) and has a slope of \( 2 \).

  2. Graph \( B(t) = 12 + 6t \):
    Starts at \( (0, 12) \) and has a slope of \( 6 \).

You will find that both lines will intersect at the point \( (6, 48) \) on the graph, confirming that they are equal in height at that point in time.