Algebra · Simultaneous equations
Chapter 1 · 4
The idea
Simultaneous equations by elimination
Why two unknowns need two equations, why adding or subtracting whole equations is legal, and the sign rule that decides which of the two kills a variable.
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Algebra · Simultaneous equations
Simultaneous equations by elimination
Why two unknowns need two equations, why adding or subtracting whole equations is legal, and the sign rule that decides which of the two kills a variable.
Why it works
Two equations, one pair
One equation with two unknowns has endless solutions — is satisfied by whole families of pairs. A SECOND equation cuts the family down to a single pair: the values that satisfy both at once. That's what "simultaneous" means — and elimination is the art of crushing the two equations into one.Engineered cancellation
If and , then adding left sides and right sides keeps truth — and look what happens to the s:Keep reading — free
The rest of the explanation, plus 2 worked examples you step through move by move.
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