For IIT aspirants #4

Algebra Level 5

The number of negative integral solutions of ( x 2 ) 2 x + 1 + 2 x 3 + 2 = ( x 2 ) 2 x 3 + 4 + 2 x 1 (x^2)2^{x+1}+2^{|x-3|+2}=(x^2)2^{|x-3|+4}+2^{x-1} is

4 6 8 1 3 2 none of them

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2 solutions

Ishan Dixit
Apr 22, 2017

Simplifying the above equation we get x 2 = ( 2 x 1 2 x 3 + 2 ) / ( 2 x + 1 2 x 3 + 4 ) x^2=( 2^{x-1} - 2^{|x-3|+2})/(2^{x+1} - 2^{|x-3|+4}) . Now on differentiating the term ( 2 x 1 2 x 3 + 2 ) / ( 2 x + 1 2 x 3 + 4 ) ( 2^{x-1} - 2^{|x-3|+2})/(2^{x+1} - 2^{|x-3|+4}) We find its derivative is always 0 0 hence its a constant function now put any value of x say 1 to find its value as 1 / 4 1/4 . Then solving x 2 = 1 / 4 x^2=1/4 we get the roots as 0.5 \boxed{0.5} and 0.5 \boxed{-0.5} . Hence it has no negative integeral solutions.

x=3 satisfies the given equation as well

Hem C - 3 years, 2 months ago
Hem C
Mar 20, 2018

First take all the terms to the other side. As x is negative, simplify the modulus with the given condition. Then take all the terms to the left hand side. Now multiply by 2^(x+1) on both sides. Now, if we factor terms out, we get the answer as x=-0.5 or x=3. Neither of which are negative integers

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