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GMAT Inequalities is a high-frequency topic in GMAT Quant, but many students struggle because the concepts behave differently from standard algebra. Understanding the right rules, patterns, and edge cases can significantly improve both speed and accuracy.- May 06
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03 Aug 2023, 03:05
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Question is 9b-3ab ÷ (9-a^2 / 3a)
When simplified becomes,
9ab(3-a)/(3-a)(3+a)
Then they cancel the (3-a) form when no constraints are given about whether a not equal to 3.
What if the (3-a) expression value is 0. Because variables can't be cancelled unless we know it's sign.
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When simplified becomes,
9ab(3-a)/(3-a)(3+a)
Then they cancel the (3-a) form when no constraints are given about whether a not equal to 3.
What if the (3-a) expression value is 0. Because variables can't be cancelled unless we know it's sign.
Posted from my mobile device
03 Aug 2023, 05:53
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When simplifying algebraic expressions, we often "cancel out" common factors in the numerator and the denominator. However, this is based on the assumption that these factors are not zero.
So, you are correct.
We should not cancel out blindly. It should depend a bit on the context as well.
For example:
If we are solving quadratic equations, it's always better not to cancel.
I have landed in trouble on a lot of questions as I cancelled out where I should not have cancelled anything.
but if the problem explicitly states that a ≠ 3, we can cancel out that term.
If nothing is stated,
a can be equal to 3,
or
a can be any other number,
we cannot cancel it.
(I'm not an expert, so let me know if there are any errors in my explanation)
So, you are correct.
We should not cancel out blindly. It should depend a bit on the context as well.
For example:
If we are solving quadratic equations, it's always better not to cancel.
I have landed in trouble on a lot of questions as I cancelled out where I should not have cancelled anything.
but if the problem explicitly states that a ≠ 3, we can cancel out that term.
If nothing is stated,
a can be equal to 3,
or
a can be any other number,
we cannot cancel it.
(I'm not an expert, so let me know if there are any errors in my explanation)
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