Compute ( 4 4 + 3 2 4 ) ( 1 6 4 + 3 2 4 ) ( 2 8 4 + 3 2 4 ) ( 4 0 4 + 3 2 4 ) ( 5 2 4 + 3 2 4 ) ( 1 0 4 + 3 2 4 ) ( 2 2 4 + 3 2 4 ) ( 3 4 4 + 3 2 4 ) ( 4 6 4 + 3 2 4 ) ( 5 8 4 + 3 2 4 )
Please don't use a calculator. (AIME question)
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How do you know that the equation can be written like that, from step one to step two
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A short derivation of the Sophie-Germain Identity is:
a 4 + 4 b 4 = a 4 + 4 a 2 b 2 + 4 b 4 − 4 a 2 b 2 = ( a 2 + 2 b 2 ) 2 − ( 2 a b ) 2 = ( a 2 + 2 a b + 2 b 2 ) ( a 2 − 2 a b + 2 b 2 )
The Sophie-Germain Identity.
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Like how do we know that the given product can be written as that
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@Trevor Arashiro – how u did the first step..plz explain it
I meant the step before that
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@Trevor Arashiro – Experience leads to good observations.
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@Joshua Ong – Come to realize it, your right, I understand it now. That's a lot of math: pure observation.
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@Trevor Arashiro – what do u think the minimum standard and age required to do this?
You use the Sophie Germain Identity to convert the first step to the second step. (By substituting 1 0 + 1 2 r = a and 3 = b for the numerator and 4 + 1 2 r = a and 3 = b for the denominator)
how did you do the first step???????????????????
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Realise that 1 0 = 1 0 + 1 2 ( 0 ) , 2 2 = 1 0 + 1 2 ( 1 ) , 3 4 = 1 0 + 1 2 ( 2 ) , … that's how you get the 1 0 + 1 2 r and r = 0 , 1 , 2 , 3 , 4 in the pi product sign
Or rather step 0
awesome .!
What if I never knew sophai German equation
Can u solve in a difrent way or ways?
I didn't know SG stands for SinGapore!! It stands for @Satvik Golechha and yes Sophie-Germain!!
Well, we can also do it like the way that this series telescope and so, it will be (3730/10) = 373
how did you get 61^2 in the last step
excellent solution
A bit confusing considering that i haven't learned this yet. But are you sure you did not skip anything?
good work battacharya
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The given product can be written as:
r = 0 ∏ 4 ( 4 + 1 2 r ) 4 + 4 ( 3 ) 4 ( 1 0 + 1 2 r ) 4 + 4 ( 3 ) 4
Now we shall use the Sophie Germain Identity
a 4 + 4 b 4 = ( a 2 + 2 b 2 + 2 a b ) ( a 2 + 2 b 2 − 2 a b )
to obtain:
r = 0 ∏ 4 ( ( 4 + 1 2 r ) 2 + 2 ( 3 ) 2 + 2 × 3 × ( 4 + 2 r ) ) ( ( 4 + 1 2 r ) 2 + 2 ( 3 ) 2 − 2 × 3 × ( 4 + 2 r ) ) ( ( 1 0 + 1 2 r ) 2 + 2 ( 3 ) 2 + 2 × 3 × ( 1 0 + 2 r ) ) ( ( 1 0 + 1 2 r ) 2 + 2 ( 3 ) 2 − 2 × 3 × ( 1 0 + 2 r ) )
= r = 0 ∏ 4 ( 1 4 4 r 2 + 1 6 8 r + 5 8 ) ( 1 4 4 r 2 + 2 4 r + 1 0 ) ( 1 4 4 r 2 + 3 1 2 r + 1 7 8 ) ( 1 4 4 r 2 + 1 6 8 r + 5 8 )
= r = 0 ∏ 4 ( 1 2 r + 1 ) 2 + 9 ( 1 2 ( r + 1 ) + 1 ) 2 + 9
= 1 2 + 9 6 1 2 + 9
= 3 7 3