14. Izzie is trying to solve this inequality: 3(t+1)−4t≥−5


After she solves it, she shows it to you and asks you if she did it correctly.

This is the work she completed:

Step 1: 3t+3−4t≥−5

Step 2: −t+3≥−5

Step 3: −t≥−2

Step 4: t≤2



(12 points)
True False
Izzie made a mistake going from step 2 to step 3

Izzie made a mistake going from step 3 to step 4

The correct answer should have been t≤8

Izzie made a mistake going from step 1 to step 2

Izzie made no mistakes in solving this inequality

Izzie should not have changed the inequality symbol from ≥
to ≤

1 answer

Let's go through Izzie's work step-by-step to determine if she made any mistakes.

Starting with the original inequality: \[ 3(t + 1) - 4t \geq -5 \]

Step 1: Distribute and combine like terms

Izzie rewrote this as: \[ 3t + 3 - 4t \geq -5 \] which simplifies to: \[ -t + 3 \geq -5 \]

This step is correct.

Step 2: Move constant terms to the right

From: \[ -t + 3 \geq -5 \] Izzie went to: \[ -t \geq -5 - 3 \] or: \[ -t \geq -8 \] but she wrote: \[ -t + 3 \geq -5 \] to: \[ -t \geq -2 \]

This step contains a mistake. She should have subtracted 3 from both sides, leading to: \[ -t \geq -8 \]

Step 3: Flip the inequality sign when multiplying/dividing

Izzie started with: \[ -t \geq -2 \] and moved to: \[ t \leq 2 \] This is incorrect because, starting from the corrected inequality \( -t \geq -8 \), when dividing by -1, the inequality sign flips: \[ t \leq 8 \] Thus, she made a mistake here.

Summary of responses:

  • Izzie made a mistake going from step 2 to step 3: True
  • Izzie made a mistake going from step 3 to step 4: True (as it's based on an earlier mistake)
  • The correct answer should have been \( t \leq 8 \): True
  • Izzie made a mistake going from step 1 to step 2: False
  • Izzie made no mistakes in solving this inequality: False
  • Izzie should not have changed the inequality symbol from \( \geq \) to \( \leq \): True (but this is a consequence of making a mistake when solving)

In conclusion, Izzie made mistakes in her solution, particularly in Step 2 and Step 3, and the correct answer should be \( t \leq 8 \).