Data Sufficiency

1.Find the value of X

stmt : 1 sqrt(X)=X-2

Solve for x will result in X=4 or X=1
But, if we substitute X=1 in the original equation, sqrt(1)=1-2
1=-1 which is incorrect.

Do we need to ignore the value of X=1 and conclude that value of X=4. Is this true always in GMAT.

For Example, in this DS question, Can we say that value of X=4, and the statement: sqrt(X)=X-2 yields single value for X.


2. Find the value of N

stmt 1: |N+9|-3N=3

Solve for N will result in N=3 or N=-3
But, if we substitute N=-3 in the original equation, |(-3)+9|-3(-3)= 6+9 =15; The stmt 1 says it is equal to 3;
15#3

Do we need to ignore the value of N=-3 and conclude that value of N=3. Is this true always in GMAT.

For Example, in this DS question, Can we say that value of N=3, and the statement: |N+9|-3N=3 yields single value for N.


Experts please advice me on this.