If x=2y and y=0, what is the value of (x+2y)−(2x+y)?
A number or a short expression. Spacing and $ signs are ignored.
Solution
We simplify first, then substitute x=2y: (x+2y)−(2x+y)=x+2y−2x−y=y−x=y−2y=−y. Alternatively, we could substitute first, then simplify: (x+2y)−(2x+y)=(2y+2y)−(2(2y)+y)=4y−5y=−y.
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