Find the sum of all integers that satisfy these conditions:\( |x|+1>7\text{ and }|x+1|\le7. \)

 Jul 23, 2020

The answer should be 0: here is why.

Here is a question for you to think about: Is the absolute value just for positive integers, or for both sides of 0?

In other words, if one number works, then it's negation will to, since the absolute value will be the same.

Therefore, if you add all those 0s up, you will get 0.


(If I'm wrong about this, please let me know!)

 Jul 24, 2020

Hmm... It says its incorrect. But i'm not sure why..

AnimalMaster  Jul 24, 2020

Oh! Okay I see. So, the integers MUST be negative for this to work out, or else they will not make any sense. So, we should find the range of both equations and use the overlap.


The range of |x| + 1 > 7 is (-inf, -6) U (6, inf)

The range of |x+1| <= 7 is [-8, 6]. 

Therefore, the only values that work are -8 and -7. So, the answer would be -15.

ilorty  Jul 24, 2020

Yay! That is correct! Thank you so much!

AnimalMaster  Jul 24, 2020

No problem!

If you don't understand how I found the ranges, just ask me :)

ilorty  Jul 24, 2020
edited by ilorty  Jul 24, 2020

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