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 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!