suminha wrote:
Hi Brent, thank you for clear and well organized approach.
I solve this question thinking this way,
x+(-y+1) vs x+(y-1) who’s bigger?
(1) don’t know how’s y, thus insufficient
(2) think y<0 with few case of when x<0 or x>0, we see who’s the winner.
I got through this risky time consuming way, because I’ve been thought that we should not deduct or add in inequality when there is no infos about their signs.
For example, 5+x > 3+x
If x is 10, 15 > 13. If x is -10, -5 < -3. So things change over what x is...
I am so confused when every time I face this kind of problems ?
Please help my poor brain..??
Thank you in advance ?
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When dealing with inequalities, we can add or subtract ANY values we want without altering the inequality.
Problems arise when we MULTIPLY or DIVIDE both sides of an inequality by a VARIABLE when we don't know whether that variable is positive or negative.
This is covered in the following video:
https://www.gmatprepnow.com/module/gmat ... /video/979Quote:
For example, 5+x > 3+x
If x is 10, 15 > 13. If x is -10, -5 < -3. So things change over what x is...
Your calculations above are not correct.
If x = -10, then 5+x > 3+x becomes 5+(-10) > 3+(-10), which simplifies to be -5 > -7, which is correct.
In fact, the left side of the inequality will ALWAYS be greater, regardless of the value of x.
We I know this because we can take: 5+x > 3+x
And subtract x from both sides to get: 5 > 3
This tells us the left side of the inequality will ALWAYS be greater, regardless of the value of x.
Does that help?
Geez I’m so embarrassed.. How can I miscalculate a simple equation...?
Thank you so much for answering me. It helps me a lot ! You made it clear