Lesson video
Start here.
Press play for Thursday’s lesson on one-step equations with negatives. Then try one yourself further down the page and finish with the Mission.
October · Week 1 · Day 4
One-Step Equations with Negatives
The minus sign is part of the number, not a decoration. Today you divide by a negative, keep every sign attached, and find out what a lone minus in front of a variable really means.
Three things to lock in.
These are the ideas the Mission asks you to use.
Negative coefficientIn −3x the coefficient is −3, minus included. Divide by the whole thing.
Sign rulesNegative divided by negative is positive. Positive divided by negative is negative.
A lone minus−x means −1x. There is a 1 hiding in there.
? Today’s Try It
Solve −5k = 35.
Two answers went up on the board. Work it out before you pick one.
✗ A: k = 7
✓ B: k = −7
✓ CHECK: −5(−7) = 35
Divide both sides by the whole −5. Positive divided by negative is negative, and the check lands back on 35.
Free Mission
Ready to try it yourself?
Thursday’s Mission has 10 problems plus the Mission Debrief so you can check your reasoning when you finish.
No sign-up required.