How to check your own work in algebra
Algebra is one of the few subjects where you can almost always prove your own answer right or wrong. Leave a minute per problem for checking and you'll catch a lot of lost points.
1. Plug your answer back in
Solved 5x − 4 = 2x + 11 and got x = 5? Substitute: 5(5) − 4 = 21 and 2(5) + 11 = 21. Both sides match, so it's right. If they don't match, the mistake is somewhere in your steps.
2. Test a number for inequalities
Got x < −3? Pick a number that fits, like −4, and check that it works in the original inequality. Then pick one that shouldn't, like 0, and confirm it fails. This catches a forgotten sign flip instantly.
3. Check both answers of a quadratic
Quadratics usually have two solutions. Substitute each one separately — it's common to get one right and one wrong.
4. Scan for sign slips
Most algebra mistakes are signs: a negative that wasn't distributed, a minus dropped when moving a term. Reread each line asking only, "Did every sign come through?"
Practice with these
- Solving with variables on both sidesMove all x terms to one side before solving.
- Flipping the inequality when dividing by a negativeMultiplying or dividing by a negative reverses the inequality.
- Solving quadratics with the zero-product ruleSet the equation to zero, factor, then set each factor to zero.
Save the steps you miss. Practice them before your test.
Sugar walks you through homework and brings back what you missed. Free, no card.
Start freeA ready-to-paste post tailored to this article.
A founder-free, viral-ready post for this article.
- 2026-09-29
How to study for a math test in 3 days
Three days is enough if you stop re-reading notes and start doing problems. Here's a day-by-day plan that puts your time where your mistakes are.
- 2026-09-29
Why you forget math steps (and how to fix it)
It made sense when the teacher did it. Two weeks later it's gone. That's normal — here's why, and what actually makes steps stick.
Homework that ends. Misses that return.