DS ! i dont understand wat is it about

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vishubn: Legendary Member; Posts: 574; Joined: Sun Jun 01, 2008 8:48 am; Location: Bangalore; Thanked: 28 times

DS ! i dont understand wat is it about

by vishubn » Fri Oct 03, 2008 5:46 am

If x(x - 5)(x + 2) = 0, is x negative?
(1) x2 – 7x ≠ 0
(2) x2 –2x –15 ≠ 0
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
3
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is
sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

vishu

Quote

Source: Beat The GMAT — Problem Solving | Fri Oct 03, 2008 5:46 am

shilpasetty: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Fri Jul 11, 2008 9:45 am

by shilpasetty » Fri Oct 03, 2008 6:19 am

If x(x - 5)(x + 2) = 0, is x negative?
(1) x2 – 7x ≠ 0
(2) x2 –2x –15 ≠ 0

1. x2 – 7x ≠ 0
can be factorised as x(x-7)≠0 i.e x≠0,7
This leaves us with 2 choices for x which is 5 and -2
So, not sufficent

2. x2 –2x –15 ≠ 0
can be factorised as (x+3)(x-5)≠0 i.e x≠-3,5
This leaves us again with 2 choices for x 0 and -2
Not sufficient.

Taking 1 and 2 together, x≠0,7,-3,5
So, it can be deduced that x= -2
Sufficient.
I think the ans is C. Correct me if I'm wrong.