What you’ll learn
Solve systems by elimination.
Key idea
The combined x coefficient remains; divide by it before back-substitution.
Cancellation removes y terms, not the combined x coefficient.
Worked example
Enter the exact value or ordered values in the format requested below.
Solve by elimination: 2x-4y=-20; 2x+4y=4. Enter ordered pair (x,y).
- Add complete equations; opposite y coefficients cancel: 4x=-16.
- Divide by 4 to obtain x=-4; substitute into either original constraint for y=3. Check pair (-4,3) in both.
Answer: (-4,3)
Quick Check
Evaluate a worked attempt at solve systems by elimination, identify the first invalid step, and provide the correction.
Solve 2x-4y=-6; 2x+4y=2. Step 1 adds equations correctly: 4x=-4. Step 2 claims x=-4 without division. Identify first invalid step and correct the pair.