There's no general forum for posting general math doubts, so posting it here.
Have a doubt with regards to mods..
say Question is squareroot[(x-5)^2]=5-x?
Now,
since on gmat, squareroot of negative numbers don't exist, this Question can be rephrased as
is (x-5) > 0?
or x>5?--------------1
but
since squareroot[(x-5)^2] is |(x-5)|, Question can be rephrased as
is |(x-5)|=5-x?
now since |(x-5)| cant be negative,
it can again be rephrased as
is 5-x>=0?
which is
is 5>=x?
or
is x<=5?------------2
How can there be 2 ( 1 & 2) interpretations ? I guess I am missing something here ... Please help..
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2 conflicting interpretations/rephasings of a Question?
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Jim@StratusPrep
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Answer:
x <= 5
This is the only way to keep the right side of the equation positive.
x <= 5
This is the only way to keep the right side of the equation positive.
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This isn't right, because you aren't taking the square root of (x-5) here. You're taking the square root of (x-5)^2, and that simply can never be negative. You do, however, know that √(anything) can never produce a negative result. So if √(anything) = 5 - x, then 5 - x must be greater than or equal to zero.sachindia wrote:
say Question is squareroot[(x-5)^2]=5-x?
Now,
since on gmat, squareroot of negative numbers don't exist, this Question can be rephrased as
is (x-5) > 0?
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