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grater than 2 and smaller than 400

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grater than 2 and smaller than 400

by sanju09 » Sat Jun 19, 2010 2:05 am
For how many integer values of n will the value of the expression 2 n^2 + 1 be an integer grater than 2 and smaller than 400?
(A) 14
(B) 15
(C) 16
(D) 28
(E) 32
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by kvcpk » Sat Jun 19, 2010 2:22 am
sanju09 wrote:For how many integer values of n will the value of the expression 2 n^2 + 1 be an integer grater than 2 and smaller than 400?
(A) 14
(B) 15
(C) 16
(D) 28
(E) 32
For any integer value of n, n^2 is positive..
So, 2 n^2 + 1 is always greater than 2. except for n= 0

2n^2 +1 <400
2n^2 <399
n^2<199
so n should be less than or equal to 14 or greater than or equal to -14 [14^2 = 196]

so total possible values for n should be 28 [excuding 0]

D
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by amising6 » Sat Jun 19, 2010 2:47 am
sanju09 wrote:For how many integer values of n will the value of the expression 2 n^2 + 1 be an integer grater than 2 and smaller than 400?
(A) 14
(B) 15
(C) 16
(D) 28
(E) 32
2 n^2 + 1<400
2n^2<399
n^2<199 (approx)
now all the number whose square less than 199
14 ^2 =196
and it will have to be greate than 2
so answer will include all the number between 1 and 14 so 14
so answer A
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by sanju09 » Sat Jun 19, 2010 2:54 am
amising6 wrote:
sanju09 wrote:For how many integer values of n will the value of the expression 2 n^2 + 1 be an integer grater than 2 and smaller than 400?
(A) 14
(B) 15
(C) 16
(D) 28
(E) 32
2 n^2 + 1<400
2n^2<399
n^2<199 (approx)
now all the number whose square less than 199
14 ^2 =196
and it will have to be greate than 2
so answer will include all the number between 1 and 14 so 14
so answer A
For integer n and 2 n^2 + 1 > 2, n cannot take 0; hence, on the number line, all integers from -14 to 14 EXCEPT 0 fulfill the need. Is it still A, man?
The mind is everything. What you think you become. -Lord Buddha



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The Princeton Review - Manya Abroad
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www.manyagroup.com
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by amising6 » Sat Jun 19, 2010 2:57 am
sanju09 wrote:
amising6 wrote:
sanju09 wrote:For how many integer values of n will the value of the expression 2 n^2 + 1 be an integer grater than 2 and smaller than 400?
(A) 14
(B) 15
(C) 16
(D) 28
(E) 32
2 n^2 + 1<400
2n^2<399
n^2<199 (approx)
now all the number whose square less than 199
14 ^2 =196
and it will have to be greate than 2
so answer will include all the number between 1 and 14 so 14
so answer A
For integer n and 2 n^2 + 1 > 2, n cannot take 0; hence, on the number line, all integers from -14 to 14 EXCEPT 0 fulfill the need. Is it still A, man?
no dude my case was only for positve integer
if you include negative integr it will be 28

thanks
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