ACT Preparation / Unit 9 ACT 0826 short lesson, about 20 seconds
Substitution
Captions available
The idea
Substitution solves a system by solving one equation for one variable and substituting that expression into the other equation.
In practice
y = x + 2 and 3x + y = 14: 3x + x + 2 = 14, so x = 3 and y = 5.
Where people slip
Substitute into the other equation, not the one you solved; using the same one gives an identity.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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