GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 14 Oct 2019, 14:02

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# What is the value of x, for which the quadratic expression, ..........

Author Message
TAGS:

### Hide Tags

e-GMAT Representative
Joined: 04 Jan 2015
Posts: 3074
What is the value of x, for which the quadratic expression, ..........  [#permalink]

### Show Tags

16 Jan 2019, 02:11
00:00

Difficulty:

35% (medium)

Question Stats:

75% (01:43) correct 25% (01:22) wrong based on 76 sessions

### HideShow timer Statistics

GMAT Club Legend
Joined: 18 Aug 2017
Posts: 4987
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE: Marketing (Energy and Utilities)
Re: What is the value of x, for which the quadratic expression, ..........  [#permalink]

### Show Tags

16 Jan 2019, 02:36
Use plug in technique
out of given options a -8 gives min value i.e 36
IMO A

EgmatQuantExpert wrote:
What is the value of x, for which the quadratic expression, $$x^2 + 16x + 100$$, takes the minimum possible value?

A. -8
B. -4
C. 0
D. 4
E. 8

_________________
If you liked my solution then please give Kudos. Kudos encourage active discussions.
Manager
Joined: 01 May 2017
Posts: 82
Location: India
Re: What is the value of x, for which the quadratic expression, ..........  [#permalink]

### Show Tags

16 Jan 2019, 02:42
x2+16x+100

1) by optional verification
-8 has the least value

2) Differentiating equation w.r.t x, to get the min
2x+16 = 0
x = -8

Option A is correct
Senior Manager
Joined: 13 Feb 2018
Posts: 453
GMAT 1: 640 Q48 V28
Re: What is the value of x, for which the quadratic expression, ..........  [#permalink]

### Show Tags

16 Jan 2019, 04:56
If we observe carefully:
$$x^2$$+16x+100=$$x^2$$+16x+64+36=$$(x+8)^2$$+36
As $$(x+8)^2$$ minimum value can be 0
$$(x+8)^2$$=0
x=-8

Imo
Ans: A
e-GMAT Representative
Joined: 04 Jan 2015
Posts: 3074
Re: What is the value of x, for which the quadratic expression, ..........  [#permalink]

### Show Tags

18 Jan 2019, 01:38

Solution

Given:
• A quadratic expression, $$x^2 + 16x + 100$$

To find:
• The minimum value of the given expression

Approach and Working:
• $$x^2 + 16x + 100 = x^2 + 16x + + 64 + 36 = (x^2 + 2 * 8 * x + 8^2) + 36$$
• $$(x^2 + 2 * 8 * x + 8^2) + 36$$ can be written as $$(x + 8)^2 + 36$$

The minimum value of $$(x + 8)^2 = 0$$, since, it cannot be negative for any value of x.
• Thus, the minimum value of $$x^2 + 16x + 100 = (x + 8)^2 + 36 = 0 + 36 = 36$$
• And, it occurs when x + 8 = 0

Therefore, x = -8

Hence the correct answer is Option A.

_________________
Re: What is the value of x, for which the quadratic expression, ..........   [#permalink] 18 Jan 2019, 01:38
Display posts from previous: Sort by