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?

Answer 1

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

Explanation:

simplified other person's answer

Answer 2

When you solve an inequality, you should always be extra careful to check that you don't multiply it by a negative number - because if you do, then you have to change the sign!

So here, the mistake is in this step:
−9x≥ −36

x ≥ 1.

you should change the sign to ≥

x≤1!