Series

Number Theory Level 2

Find the number in place of ?

4 (25) 3, 21 (1225) 28, 6 (?) 8


The answer is 100.

Anuj Shikarkhane by Anuj Shikarkhane , 19, India

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2 solutions

Kenny Lau
Jul 8, 2014

25 = 4 2 + 3 2 1225 = 2 1 2 + 2 8 2 ? = 6 2 + 8 2 = 100 \begin{array}{rcl} 25&=&4^2+3^2\\ 1225&=&21^2+28^2\\ ?&=&6^2+8^2&=&100 \end{array}

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Avinash Bagale
Jun 22, 2014

Its really easy 1st of all get multiplication of both the Numbers and then again multiple it by 2 after that add the Square subtraction of those numbers See 6 8=48 48 2=96 (8-6)^2=(2)^2=4 96+4=100 and done

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Ok, formatting stuff, you meant 6 × 8 = 48 , 48 × 2 = 96 6\times8=48,48\times2=96 ...

Therefore the formula is a ⋅ b = 2 a b + ( b − a ) 2 = a 2 + b 2 a\cdot b=2ab+(b-a)^2=a^2+b^2 .

You have over-complicated the business xD

Kenny Lau - 6 years, 11 months ago

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