Solve for r
r=0
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1r=0-2r
Combine -r and -r to get -2r.
1r=-2r
Anything plus zero gives itself.
1r+2r=0
Add 2r to both sides.
3r=0
Combine 1r and 2r to get 3r.
r=0
Product of two numbers is equal to 0 if at least one of them is 0. Since 3 is not equal to 0, r must be equal to 0.
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Matrix
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Limits
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