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What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ?

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What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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New post 03 Mar 2014, 01:16
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The Official Guide For GMAT® Quantitative Review, 2ND Edition

What is the value of \(2x^2 - 2.4x - 1.7\) for \(x = 0.7\) ?

(A) -0.72
(B) -1.42
(C) -1.98
(D) -2.40
(E) -2.89

Problem Solving
Question: 121
Category: Algebra Simplifying algebraic expressions
Page: 77
Difficulty: 600


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Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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New post Updated on: 14 Jul 2014, 21:23
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Answer = D = -2.4

\(2x^2 - 12.4x - 1.7\)

\(2x(x - 1.2) - 1.7\)

Placing the value x = 0.7

2 . 0.7 (-0.5) - 1.7

-0.7 - 1.7

= -2.4
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Originally posted by PareshGmat on 03 Mar 2014, 02:33.
Last edited by PareshGmat on 14 Jul 2014, 21:23, edited 2 times in total.
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Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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New post 03 Mar 2014, 20:08
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[2(7)(7)-24(7)-170]/100
=-2.4
D
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Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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New post 03 Mar 2014, 21:37
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2(0.7)^2 - 2.4(0.7) - 1.7
= 2(0.49) - 1.68 - 1.7
= 0.98 - 1.68 - 1.7
= -2.4

Ans is (D)
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Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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New post 04 May 2015, 13:30
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2*49*10^(-2) - 24*7*10^(-2) - 170*10^(-2) = -240*10^(-2) = -2,4

Update
\(x(2x-2,4)-1,7 = 0,7(1,4-2,4)-1,7 = -0,7-1,7=-2,4\)
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Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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New post 06 May 2016, 08:25
Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND Edition

What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ?

(A) -0.72
(B) -1.42
(C) -1.98
(D) -2.40
(E) -2.89

Problem Solving
Question: 121
Category: Algebra Simplifying algebraic expressions
Page: 77
Difficulty: 600


GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition - Quantitative Questions Project

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We'll be glad if you participate in development of this project:
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2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
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Thank you!


\(2x^2\) - \(2.4x\) - 1.7 ; given x = 0.7

Or, \(2(0.7)^2\) - \(2.4(0.7)\) - \(1.7\)

Or, \(2(0.49)\) - \(2.4(0.7)\) - \(1.7\)

Or, \(0.98\) - \(1.68\) - \(1.7\)

Or, \(- 2.40\)

Hence answer will be (D)
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Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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New post 06 May 2016, 09:55
[quote="Bunuel"]The Official Guide For GMAT® Quantitative Review, 2ND Edition

What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ?

(A) -0.72
(B) -1.42
(C) -1.98
(D) -2.40
(E) -2.89


2*0.7*0.7-2.4*0.7-1.7
.98-1.68-1.7
=-2. 40
answer D
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Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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New post 28 May 2016, 11:04
\(2 * \frac{7}{10}* \frac{7}{10}- 2.4 * \frac{7}{10}- 1.7\)

= \(\frac{49}{50} - 2.4 * 10 *\frac{7}{10 * 10}- 1.7 * \frac{10}{10}\)

= \(\frac{49}{50} - 24 *\frac{7}{100}- \frac{17}{10}\)

= \(\frac{49}{50} - \frac{42}{25} - \frac{17}{10}\)

=\(\frac{98-168-170}{100}\)

= -2.4
=Answer D.
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Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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New post 26 Jul 2017, 16:42
Quote:

What is the value of \(2x^2 - 2.4x - 1.7\) for \(x = 0.7\) ?

(A) -0.72
(B) -1.42
(C) -1.98
(D) -2.40
(E) -2.89


Substituting 0.7 for x, we have:

2(0.7)^2 - 2.4(0.7) - 1.7

2(0.49) - 1.68 - 1.7 = 0.98 - 1.68 - 1.7 = -2.4

Alternate Solution:

Let’s factor the expression 2x^2 - 2.4x - 1.7:

2x^2 - 2.4x - 1.7 = (x - 1.7)(2x + 1)

Now, substituting x = 0.7 in the factored expression, we get (0.7 - 1.7)(2(0.7) + 1) = (-1)(1.4 + 1) = -2.4.

Answer: D
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Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ? [#permalink]

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New post 25 Dec 2017, 05:00
Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND Edition

What is the value of \(2x^2 - 2.4x - 1.7\) for \(x = 0.7\) ?

(A) -0.72
(B) -1.42
(C) -1.98
(D) -2.40
(E) -2.89

Problem Solving
Question: 121
Category: Algebra Simplifying algebraic expressions
Page: 77
Difficulty: 600


GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition - Quantitative Questions Project

Each week we'll be posting several questions from The Official Guide For GMAT® Quantitative Review, 2ND Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project:
1. Please provide your solutions to the questions;
2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Thank you!


2x^2-2.4x-1.7
=> x(2x-2.4)+1.7
=> substituting x=0.7
=> 0.7(2*0.7-2.4)+1.7
=> 0.7(1.4-2.4)+1.7
=> 0.7(-1)+1.7
=> -0.7-1.7
=> -2.4

Therefore 'D'

Thanks
Dinesh
Re: What is the value of 2x^2 - 2.4x - 1.7 for x = 0.7 ?   [#permalink] 25 Dec 2017, 05:00
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