SAT Math: Solving Systems by Elimination
32+ practice questions in Praczo
The concept, explained
- 1
Elimination adds or subtracts equations to cancel one variable, leaving one solvable equation.
- 2
To eliminate a variable, its coefficients must be equal (or opposite). If not, multiply one or both equations by a constant first.
- 3
Add the equations when coefficients have opposite signs; subtract when they have the same sign.
- 4
After finding one variable, substitute back into either original equation to find the other.
- 5
Elimination is fastest when both equations are in Ax + By = C form and coefficients are easy to match.
- ✗ Forgetting to multiply every term in the equation, not just the variable being eliminated.
- ✗ Subtracting incorrectly when signs are involved — be especially careful with negative coefficients.
SAT-style practice
3x + 2y = 16 and 3x − y = 7. What is the value of y?
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