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Substitution is the idea that when we have an expression or equation, we can swap out the letter for a given number. In expressions, this means we can use order of operations to simplify down to ONE TERM (typicaly a number).
OR
If we have a 2 variable equation, we can substitute a value for one letter (x) and solve for the other letter (y).
If this was the question...
"Evaluate y = x + 3 when x = 5"
we need to change the x to the number given...5
rewrite the question y = 5 + 3, then solve... y = 8
EASY
MEDIUM
HARD!
we use substitution to find y-values in our xy t-charts!
we have a 2 variable equation,
y = x + 3
and want to graph it.
Try to make an x/y t-chart for these 1 step equations...
y = x - 5 y = x + 10 y = x -1
and these...
y = 2x y = -5x y = 7x y = -x
and these...2 step equations...
y = 2x + 4 y = 5x - 3 y = x + 1 y = x - 1
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