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4^1/2 is the same as Sqr Rt of 4sushanta57021 wrote:Let X = -2
[-(-2){-2}]^1/2
2*2^1/2
4^1/2
2
Note: {}=Absolute value
So x = -x
But 4^1/2 can be +2 or -2.
hence answer can be +X or -X.
please explain.......
sushanta57021 wrote:sorry for posting it twice, but first i posted it in the wrong forum, i.e DS forum.
But anyway, I am not convinced with the answer yet.
We cann't take -X as answer only because X<0.
let me explain:
Say, P = [-X{abs(X)}]^1/2
is there any reason why P has to be positive? P can be negetive also, that means p can be X.
Can some one please clarify?
P = [-X{abs(X)}]^1/2iamcste wrote:sushanta57021 wrote:sorry for posting it twice, but first i posted it in the wrong forum, i.e DS forum.
But anyway, I am not convinced with the answer yet.
We cann't take -X as answer only because X<0.
let me explain:
Say, P = [-X{abs(X)}]^1/2
is there any reason why P has to be positive? P can be negetive also, that means p can be X.
Can some one please clarify?
Momentarily forget P is positive or negative
we know that x is negative, hence abs(X)=-X
Say, P = [-X{abs(X)}]^1/2
= [-X{-X}]^1/2
= (X^2)^1/2
= square root of ( square of X)
=+ X or -X
But, we know that X is negative no
hence P=-X
( If this is understood, forget what P has to be before calculating and confusion arised from here
when you posted the question in DS, you forgot to mention X <0
Check here
https://www.beatthegmat.com/algebra-t22735.html
hence Logitech said that since outer bracket in solving P is a square root
square root of only positive no is defined
this means he concluded abs(X) was negative
this in turn meant X was negative
This he did since you didnot mention X is negative
Had he known that he would not have done reverse calcns
Well, i understand your confusion.sushanta57021 wrote:sorry for posting it twice, but first i posted it in the wrong forum, i.e DS forum.
But anyway, I am not convinced with the answer yet.
We cann't take -X as answer only because X<0.
let me explain:
Say, P = [-X{abs(X)}]^1/2
is there any reason why P has to be positive? P can be negetive also, that means p can be X.
Can some one please clarify?
first of all there is a serious flaw in your explanation. see the highlighted text. i think you didn't get the point of my confusion.jimmiejaz wrote:Well, i understand your confusion.sushanta57021 wrote:sorry for posting it twice, but first i posted it in the wrong forum, i.e DS forum.
But anyway, I am not convinced with the answer yet.
We cann't take -X as answer only because X<0.
let me explain:
Say, P = [-X{abs(X)}]^1/2
is there any reason why P has to be positive? P can be negetive also, that means p can be X.
Can some one please clarify?
But, sqrt(-ve number) gives us a complex number.
Here we are given that x<0.
Lets go according to you,
P = sqrt(-4) assuming x=2, can u get a definite solution for it. No.
So, when we are given x<0, we have to take x as negative and then solve else we cant get answer in the choices mention and complex numbers are indeed out of scope of GMAT land.
I hope your confusion in cleared.....
Rajiv
No...your solution does not stand.jimmiejaz wrote:we are given p = sqrt(-x|x|) where x<0
lets go by ur approach that soln is +x, it shall satisfy the equation.
p = sqrt(-x.x) since we took the solution as +x
p = sqrt(-x^2)
now, tell me how will you solve this as p = +x?
Hope you get the point now. That if we put the values and backsolve, only -x will give us answer. Hope it helps.
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