Eduardo solved the following inequality and his work is shown below:

−5(x + 4) + 21 ≥ −3 + 4(x − 8)
−5x − 20 + 21 ≥ −3 + 4x − 32
−5x + 1 ≥ 4x − 35
−9x ≥ −36
x ≥ 1

What mistake did Eduardo make in solving the inequality?

When dividing by −9, he did not change the ≥ to ≤.

He subtracted 4x from both sides when he should have added 5x.

He subtracted 1 from both sides when he should have added 36.

He did not make a mistake.

@plohrr @april115

Question

Eduardo solved the following inequality and his work is shown below:

−5(x + 4) + 21 ≥ −3 + 4(x − 8)
−5x − 20 + 21 ≥ −3 + 4x − 32
−5x + 1 ≥ 4x − 35
−9x ≥ −36
x ≥ 1

What mistake did Eduardo make in solving the inequality?

 When dividing by −9, he did not change the ≥ to ≤.

 He subtracted 4x from both sides when he should have added 5x.

 He subtracted 1 from both sides when he should have added 36.

 He did not make a mistake.


@plohrr @april115

anonymous · Answer

@MathLegend