root qs- 700 level, weird solution by mgmat!

[vkb16]

If sqrt{(x+4)^2} = 3, which of the following could be the value of x – 4?

-11

-7

-4

-3

5

oa is A

-----"MGMAT's solution:-
the expression can be simplified to |x + 4|, and the original equation can be solved accordingly.
If |x + 4| = 3, either x = -1 or x = -7 "-----------

why cant we just take x+4=3 => x= -1, and hence x-4=-5????
why are we taking |x+4| = 3??

[dmateer25]

I hope this helps.

[mkbigmoz]

You cant simply square the foils. You have to factor them out, then square the result, along with the answer. Then complete, result X = -1, or -7. -7-4 = -11

[vittalgmat]

If sqrt{(x+4)^2} = 3, which of the following could be
why cant we just take x+4=3 => x= -1, and hence x-4=-5????
why are we taking |x+4| = 3??

First of all, the problem is based on a principle which roughly put is:

sqrt(x^2) = |x|.

Therefore, MGMT soln does this. If u know this, the prblm becomes easy.

This problem does not look like a 700 level problem.
The problem is pretty straight forward and involves 2 steps.
IMO, this is a 600 level Q.

[vkb16]

this was labeled as 700-800 level my MGMAT CAT..

thanks for the info though...