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Comment on (x-y)/xy
Hi Brent,
Under what circumstances can we cross multiply a variable(s) with an unknown sign? Because we are not sure of the sign of xy here.
I believe you're confusing
I believe you're confusing the rules solving inequalities with the rules for solving equations.
If we're multiplying or dividing both sides of an INEQUALITY by some variable, then we need to know for the sign of that variable.
If we're multiplying or dividing both sides of an EQUATION by some variable, we don't need to know the sign of the variable. The resulting equation still holds true.
Cheers,
Brent
and this inequality rule
That's correct. That
That's correct. That inequality rule also applies to Quantitative Comparison questions.