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# If x^2 - 2x - 35 = 0 and x>0, which of the following must be equal to

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Senior Manager
Joined: 27 May 2014
Posts: 320

Kudos [?]: 193 [0], given: 83

GMAT 1: 730 Q49 V41
If x^2 - 2x - 35 = 0 and x>0, which of the following must be equal to [#permalink]

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06 Oct 2017, 06:41
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Question Stats:

81% (00:54) correct 19% (01:39) wrong based on 68 sessions

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If x^2 - 2x - 35 = 0 and x>0, which of the following must be equal to 0?

I. x^2 - 7x + 12
II. x^2 - 13x + 42
III. x^2 - 5x + 6

(a) I only
(b) II only
(c) III only
(d) II and III only
(e) I, II, and III
[Reveal] Spoiler: OA

Kudos [?]: 193 [0], given: 83

Math Expert
Joined: 02 Sep 2009
Posts: 42577

Kudos [?]: 135451 [0], given: 12695

Re: If x^2 - 2x - 35 = 0 and x>0, which of the following must be equal to [#permalink]

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06 Oct 2017, 06:44
saswata4s wrote:
If x^2 - 2x - 35 = 0 and x>0, which of the following must be equal to 0?

I. x^2 - 7x + 12
II. x^2 - 13x + 42
III. x^2 - 5x + 6

(a) I only
(b) II only
(c) III only
(d) II and III only
(e) I, II, and III

This is a copy of the following OG question: https://gmatclub.com/forum/if-x-2-2x-15 ... 67001.html
_________________

Kudos [?]: 135451 [0], given: 12695

Intern
Joined: 28 Dec 2010
Posts: 49

Kudos [?]: 10 [0], given: 7

Re: If x^2 - 2x - 35 = 0 and x>0, which of the following must be equal to [#permalink]

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08 Oct 2017, 02:31
Lets first find valid values of x
$$(x-7)(x+5) = 0 , and x> 0$$

This means x=7

Now look at
1. (x-3) (x-4)
2. (x-6) (x-7)
3. (x-2) (x-3)

Only Statement 2 would be 0.
B.
_________________

_________________________________________

Kudos [?]: 10 [0], given: 7

VP
Joined: 22 May 2016
Posts: 1119

Kudos [?]: 400 [0], given: 640

If x^2 - 2x - 35 = 0 and x>0, which of the following must be equal to [#permalink]

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08 Oct 2017, 03:31
saswata4s wrote:
If x^2 - 2x - 35 = 0 and x>0, which of the following must be equal to 0?

I. x^2 - 7x + 12
II. x^2 - 13x + 42
III. x^2 - 5x + 6

(a) I only
(b) II only
(c) III only
(d) II and III only
(e) I, II, and III

$$x^2 - 2x - 35 = 0$$
Find $$x$$

$$(x - 7)(x + 5)$$
$$x = 7$$ or $$x = -5$$
Prompt: $$x > 0$$, so $$x = 7$$

Either factor the expressions in the options, or plug $$x = 7$$ into them.

If you factor the expressions, one or both factors must be $$(x - 7)$$

Plugging in $$x = 7$$, looking for "which [option] must be equal to 0":

I. $$x^2 - 7x + 12$$
$$49 - 49 + 12 = 12$$ NO

II. $$x^2 - 13x + 42$$
$$49 - 91 + 42 = 0$$ YES

III. $$x^2 - 5x + 6$$
$$49 - 35 + 12 = 26$$ NO

Only Option II yields 0.

Kudos [?]: 400 [0], given: 640

If x^2 - 2x - 35 = 0 and x>0, which of the following must be equal to   [#permalink] 08 Oct 2017, 03:31
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# If x^2 - 2x - 35 = 0 and x>0, which of the following must be equal to

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