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In the equation X^2+bX+12=0

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evgeniailyina2018
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In the equation X^2+bX+12=0 [#permalink] New post   14 Jun 2020, 01:00
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In the equation X^2+bX+12=0, X is a variable and b is constant. What is the value of b?
(1) X-3 is a factor of X^2+bX+12
(2) 4 is a root of the equation X^2+bX+12=0
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chetan2u
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Re: In the equation X^2+bX+12=0 [#permalink] New post   14 Jun 2020, 01:09
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evgeniailyina2018 wrote:
In the equation X^2+bX+12=0, X is a variable and b is constant. What is the value of b?
(1) X-3 is a factor of X^2+bX+12
(2) 4 is a root of the equation X^2+bX+12=0


\(x^2+bx+12=0\)

(1) x-3 is a factor of x^2+bx+12
This means when x=3, the equation should give us 0 as the answer.
\(x^2+bx+12=0\)
\(3^2+3b+12=0...b=-21/3=-7\)
Sufficient

(2) 4 is a root of the equation X^2+bX+12=0
This means when x=4, the equation should give us 0 as the answer.
\(x^2+bx+12=0\)
\(4^2+4b+12=0...b=-28/4=-7\)
Sufficient

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satya2029
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Re: In the equation X^2+bX+12=0 [#permalink] New post   14 Jun 2020, 01:15
evgeniailyina2018 wrote:
In the equation X^2+bX+12=0, X is a variable and b is constant. What is the value of b?
(1) X-3 is a factor of X^2+bX+12
(2) 4 is a root of the equation X^2+bX+12=0


Since the given equation is quadratic equation,
From 1
3 is root. By putting X=3 equation becomes Y=0
9+3b+12=0
b=-7
From 2
16+4b+12=0
b=-7
D:)
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Re: In the equation X^2+bX+12=0 [#permalink] New post   14 Jun 2020, 08:37
evgeniailyina2018 wrote:
In the equation X^2+bX+12=0, X is a variable and b is constant. What is the value of b?
(1) X-3 is a factor of X^2+bX+12
(2) 4 is a root of the equation X^2+bX+12=0


Given: In the equation X^2+bX+12=0, X is a variable and b is constant.
Asked: What is the value of b?

(1) X-3 is a factor of X^2+bX+12
Putting X = 3 in the equation,
3^2 + 3b + 12 = 0
3b = - 21
b = - 7
SUFFICIENT

(2) 4 is a root of the equation X^2+bX+12=0
4^2 + 4b + 12 = 0
4b = - 28
b = - 7
SUFFICIENT

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obahr
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Re: In the equation X^2+bX+12=0 [#permalink] New post   22 Mar 2023, 04:32
Hey, i dont quit Inderstand how do you know that you have to Put in 3 in the equation for (1) ? Maybe I am getting the wording wrong for X-3 is a Factor of the equation?
Thank you so much!

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Re: In the equation X^2+bX+12=0 [#permalink]
22 Mar 2023, 04:32
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