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If x^2 + 12x + 20 < 0, how many integer values can x be?

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If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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New post 17 Mar 2011, 13:44
2
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If x^2 + 12x + 20 < 0, how many integer values can x be?

(A) 6
(B) 7
(C) 8
(D) 9
(E) 10
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Re: If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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New post 17 Mar 2011, 14:32
banksy wrote:
27. (SC) If x^2 + 12x + 20 < 0, how many integer values can x be?
(A) 6
(B) 7
(C) 8
(D) 9
(E) 10



x^2 + 12x + 20 < 0 --> (x+10)(x+2)<0 this will be true only when x<-2 and x> -10.

Ans = C
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Re: If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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New post 17 Mar 2011, 18:30
the same solution and also found -8<a<-2 and
C is the answer
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Re: If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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New post 17 Mar 2011, 22:34
1
banksy wrote:
27. (SC) If x^2 + 12x + 20 < 0, how many integer values can x be?
(A) 6
(B) 7
(C) 8
(D) 9
(E) 10


Sol:

x^2+12x+20 = x^2+10x+2x+20 = x(x+10)+2(x+10) = (x+2)(x+10)

(x+2)(x+10) < 0

Roots of x= -10,-2

Ranges; x<-10, -10<x<-2, x>-2

For x>-2, let's say x=0; (x+2)(x+10) = 2*10=20. It is a positive

Thus,
x>-2 is +ve
-10<x<-2 is -ve; alternated from previous
x<-10 is +ve; alternated from previous

For "<" sign, we must consider only -ves.

-10<x<-2 befits the value of x that satisfy the inequality.
x can be -9,-8,-7,-6,-5,-4,-3

Count=7

Ans: "B"
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Re: If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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New post 18 Mar 2011, 07:34
fluke wrote:
banksy wrote:
27. (SC) If x^2 + 12x + 20 < 0, how many integer values can x be?
(A) 6
(B) 7
(C) 8
(D) 9
(E) 10


Sol:

x^2+12x+20 = x^2+10x+2x+20 = x(x+10)+2(x+10) = (x+2)(x+10)

(x+2)(x+10) < 0

Roots of x= -10,-2

Ranges; x<-10, -10<x<-2, x>-2

For x>-2, let's say x=0; (x+2)(x+10) = 2*10=20. It is a positive

Thus,
x>-2 is +ve
-10<x<-2 is -ve; alternated from previous
x<-10 is +ve; alternated from previous

For "<" sign, we must consider only -ves.

-10<x<-2 befits the value of x that satisfy the inequality.
x can be -9,-8,-7,-6,-5,-4,-3

Count=7

Ans: "B"


how is x>-2?
i calculated x<-2, or x<-10.
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Re: If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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New post 18 Mar 2011, 08:21
Baten80 wrote:
fluke wrote:
banksy wrote:
27. (SC) If x^2 + 12x + 20 < 0, how many integer values can x be?
(A) 6
(B) 7
(C) 8
(D) 9
(E) 10


Sol:

x^2+12x+20 = x^2+10x+2x+20 = x(x+10)+2(x+10) = (x+2)(x+10)

(x+2)(x+10) < 0

Roots of x= -10,-2

Ranges; x<-10, -10<x<-2, x>-2

For x>-2, let's say x=0; (x+2)(x+10) = 2*10=20. It is a positive

Thus,
x>-2 is +ve
-10<x<-2 is -ve; alternated from previous
x<-10 is +ve; alternated from previous

For "<" sign, we must consider only -ves.

-10<x<-2 befits the value of x that satisfy the inequality.
x can be -9,-8,-7,-6,-5,-4,-3

Count=7

Ans: "B"


how is x>-2?
No, x is not greater than -2.

Please read my post closely;
-10<x<-2 befits the value of x that satisfy the inequality.
x can be -9,-8,-7,-6,-5,-4,-3


Where I mentioned; "x>-2", I was just checking the side(+ve or -ve) of the inequality for the range where "x>-2"

i calculated x<-2, or x<-10.

I am afraid, this is not correct!!! It should be;
x<-2 AND x>-10



I have incorporated following method to calculate the range;

http://gmatclub.com/forum/inequalities-trick-91482.html

I humbly suggest you go through the same.
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Re: If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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New post 18 Mar 2011, 10:32
dreambeliever wrote:
banksy wrote:
27. (SC) If x^2 + 12x + 20 < 0, how many integer values can x be?
(A) 6
(B) 7
(C) 8
(D) 9
(E) 10



x^2 + 12x + 20 < 0 --> (x+10)(x+2)<0 this will be true only when x<-2 and x> -10.

Ans = C



-10 to -2 exclusive on the number line leaves 7 integers not 8. have to quit committing this types mistakes!
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Re: If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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New post 18 Mar 2011, 16:54
solving the inequality

one solution x < -10 , x>-2 , unlimited integers can be chosen for these

second solution x >-10 , x<-2 , 7 possible integers ( -9,-8,-7...-3)

Hence the answer is B.



banksy wrote:
27. (SC) If x^2 + 12x + 20 < 0, how many integer values can x be?
(A) 6
(B) 7
(C) 8
(D) 9
(E) 10
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Re: If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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New post 18 Mar 2011, 21:57
The question asks, for how many integer values of x:

(x+10)(x+2) < 0

so -10 < x -2

only 7 integers between -10 and -2, so answer is B.
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Re: If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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New post 19 Jun 2017, 13:37
After solving the equation, we get

(x+10)(x+2)<0

-10<x<-2

So, consider all the integer values within this range = -9, -8, -7, -6, -5, -4, -3

Which gives us 7 integer values, hence answer is B
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Re: If x^2 + 12x + 20 < 0, how many integer values can x be?  [#permalink]

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