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shivaankarkumara
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x3-x=p,x=odd p divisible by 24

by shivaankarkumara Mon Jun 11, 2012 11:31 am

in number property guide 4th edition page 151

it says
p=(x-1)(x)(x+1)
if x is odd (x-1)and (x+1) even-agreed
it further says p is divisible by atleast 4
how so
q)if x is odd x can be 1
x-1=0(even)
x+1=2(even)
this is not divisile by 4
and the odd no x not divisible by 3

please explain
jnelson0612
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Re: x3-x=p,x=odd p divisible by 24

by jnelson0612 Sat Jun 16, 2012 11:20 pm

shivaankarkumara Wrote:in number property guide 4th edition page 151

it says
p=(x-1)(x)(x+1)
if x is odd (x-1)and (x+1) even-agreed
it further says p is divisible by atleast 4
how so


If x is odd, I have that p is even * odd * even. Each of those evens is divisible by 2, so each even is contributing at least one 2 to the final product. So I have even (2 * other factors) * odd * even (2 *other factors). 2*2 = 4, so p must be divisible by 4.


shivaankarkumara Wrote:q)if x is odd x can be 1
x-1=0(even)
x+1=2(even)
this is not divisible by 4
and the odd no x not divisible by 3

please explain


Actually, 0 * odd * 2 will equal 0, which is divisible by 4, because zero is divisible by all integers.
Jamie Nelson
ManhattanGMAT Instructor