Morning. I'm needing to check some of my son's test answers. Solve for s. show all steps. -3s is greater than or equal to 18.....he put -3(-6) is greater than or equal to 18...so s is greater than or equal to -6

Question

Morning.  I'm needing to check some of my son's test answers.  Solve for s. show all steps.  -3s is greater than or equal to  18.....he put -3(-6) is greater than or equal to 18...so s is greater than or equal to -6

anonymous · Answer

$$-3s \ge 18$$ Divide both sides by -3 (so flip inequality):
$$s\le -6$$
He needs to remember to flip the inequality sign whenever he multiplies/divides by a negative number.

anonymous · Answer

s has to be smaller than -6. like -7 is smaller than -6. Rest is correct.

anonymous · Answer

ok.  Thanks

anonymous · Answer

@cgliss if you want to explain to him why this happens, give him the example of -1<5.
If you multiply both sides by -1 without swapping the inequality sign around, you get 1<-5. This doesn't make sense, so you have to flip it to 1>-5.

anonymous · Answer

great example.....thanks