Inspired by Michael Fuller

Algebra Level 2

3 0 4 26 × 136 × 229 = ? 30^4-26\times 136\times 229= \ ? \


The answer is 256.

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1 solution

Adarsh Kumar
Jan 2, 2016

Well,obviously it can be done without a calculator! Motivation:When we see 3 0 4 30^4 ,we think that if we can manipulate the second part a bit to get 3 0 4 something 30^4-\text{something} ,then that "something" would be our answer,then since there is multiplication sign we get the idea of ( a b ) ( a + b ) = a 2 b 2 (a-b)(a+b)=a^2-b^2 ,and then ( a 2 b 2 ) ( a 2 + b 2 ) = a 4 b 4 (a^2-b^2)(a^2+b^2)=a^4-b^4 ,precisely what we need here a = 30 a=30 ,the first part is: 26 = ( 30 4 ) 26=(30-4) ,now we require 30 + 4 30+4 ,so we write the given expression as 3 0 4 ( 30 4 ) ( 30 + 4 ) × 4 × 229 30^4-(30-4)(30+4)\times 4\times 229 ,yup!it fits perfectly,so now we have ( 3 0 2 4 2 (30^2-4^2 ,we need 3 0 2 + 4 2 = 916 = 4 × 229 30^2+4^2=916=4\times 229 ,so 3 0 4 ( 3 0 2 4 2 ) ( 3 0 2 + 4 2 ) = 3 0 4 ( 3 0 4 4 4 ) = 4 4 = 256 30^4-(30^2-4^2)(30^2+4^2)\\ =30^4-(30^4-4^4)\\ =4^4=256 ,and done!

Moderator note:

Nice setup and usage of the identity.

yes i did same thing, figured there is a solution without cacl.

Mardokay Mosazghi - 5 years, 5 months ago

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