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3x^2 + 2x - 8 =

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Intern
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Joined: 05 May 2012
Posts: 13
3x^2 + 2x - 8 =  [#permalink]

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New post 13 May 2012, 22:53
1
1
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

73% (01:12) correct 27% (01:30) wrong based on 173 sessions

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3x^2 + 2x - 8 =

A. (3x-4)(x-2)
B. (3x-4)(x+2)
C. (3x-4)(x-2)
D. (3x-2)(x+4)
E. none of above
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Re: 3x^2 + 2x - 8 =  [#permalink]

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New post 13 May 2012, 23:15
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3x^2 + 2x - 8
= 3x^2 + 6x - 4x - 8
= 3x (x + 2) - 4 (x+2)
= (3x-4) (x+2)

Option B
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Re: 3x^2 + 2x - 8 =  [#permalink]

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New post 14 May 2012, 00:09
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Re: 3x^2 + 2x - 8 =  [#permalink]

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New post 14 May 2012, 01:05
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3x^2 + 2x - 8

X1*X2=-8/3
X1+X2=-2/3

Only option B satisfies these parameters
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3x^2 + 2x - 8 =  [#permalink]

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New post 21 Jan 2016, 07:11
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1. just open the brackets. A is out, B is in. 30 secs.

2. factoring box

a. 3x^2 + 2x - 8 -> mulptiply a and c = 3*-8 = -24
b. factors of -24 that add up to b (i.e. 2) are 6 and -4 (note that the larger factor should be positive because b is positive, one of the factors is negative)
c. arrange the box as below and find common factors in the 2 vertical and 2 horizontal lines. form equation. of (3x-4)(x+2)
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box.jpg [ 7.22 KiB | Viewed 3369 times ]


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Re: 3x^2 + 2x - 8 =  [#permalink]

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New post 04 Apr 2019, 06:22
I used quadratic equation in solving this
3x^2+2x-8=
X=-b+/- sqrt b^2-4ac/2a
Where a =3, b=2, And c=-8
X=-2+/-sqrt 2^2-4(3)(-8)/2(3)
X=-2+/-sqrt 4+96/6
X=-2+/-sqrt100/6=-2+/-10/6
X=-2+10/6 or X=-2-10/6
X=8/6=4/3 or X=-12/6=-2
Therefore X=4/3 or -2
X=4/3= 3x=4, 3x-4=0
X=-2, X+2=0
So we have 3x-4=0 or x+2=0
Final answer (3x-4)(x+2)
Answer is B

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Re: 3x^2 + 2x - 8 =  [#permalink]

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New post 04 Apr 2019, 06:27
1
I used quadratic equation in solving this
3x^2+2x-8=
X=-b+/- sqrt b^2-4ac/2a
Where a =3, b=2, And c=-8
X=-2+/-sqrt 2^2-4(3)(-8)/2(3)
X=-2+/-sqrt 4+96/6
X=-2+/-sqrt100/6=-2+/-10/6
X=-2+10/6 or X=-2-10/6
X=8/6=4/3 or X=-12/6=-2
Therefore X=4/3 or -2
X=4/3= 3x=4, 3x-4=0
X=-2, X+2=0
So we have 3x-4=0 or x+2=0
Final answer (3x-4)(x+2)
Answer is B

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20190404_142712.jpg [ 937.92 KiB | Viewed 182 times ]

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Re: 3x^2 + 2x - 8 =  [#permalink]

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New post 07 Apr 2019, 18:43
1
malkov wrote:
3x^2 + 2x - 8 =

A. (3x-4)(x-2)
B. (3x-4)(x+2)
C. (3x-4)(x-2)
D. (3x-2)(x+4)
E. none of above


Factoring the given quadratic expression, we have:

(3x - 4)(x + 2)

Answer: B
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Re: 3x^2 + 2x - 8 =   [#permalink] 07 Apr 2019, 18:43
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