Not as bad as it looks

Algebra Level 5

12 3 x 2 + 4 x 2 3 x 2 = 4 x 2 \sqrt{12-\frac{3}{x^2}}+\sqrt{4x^{2}-\frac{3}{x^2}}=4x^{2}

Find the sum of all solutions x x .


The answer is 0.

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2 solutions

Jon Haussmann
Nov 6, 2015

In the given equation, if x x is a solution, then so is x -x . Therefore, S = 0 S = 0 .

Son Nguyen
Nov 5, 2015

Ok my solution 12 3 x 2 + 4 x 2 3 x 2 = 4 x 2 \sqrt{12-\frac{3}{x^{2}}}+\sqrt{4x^2-\frac{3}{x^2}}=4x^2 Let x 2 = a > 0 x^{2}=a> 0 12 3 a + 4 a 3 a = 4 a \Rightarrow \sqrt{12-\frac{3}{a}}+\sqrt{4a-\frac{3}{a}}=4a 4 a 3 a = 4 a 12 3 a \Leftrightarrow \sqrt{4a-\frac{3}{a}}=4a-\sqrt{12-\frac{3}{a}} 4 a 3 a = 16 a 2 8 a 12 3 a + 12 3 a \Rightarrow 4a-\frac{3}{a}=16a^2-8a\sqrt{12-\frac{3}{a}}+12-\frac{3}{a} 4 a 2 2 a 12 3 a a + 3 = 0 \Leftrightarrow 4a^{2}-2a\sqrt{12-\frac{3}{a}}-a+3=0 4 a 2 a 48 a 2 12 a + 3 = 0 \Leftrightarrow 4a^{2}-a-\sqrt{48a^{2}-12a}+3=0 12 a ( 4 a 1 ) 12 12 a ( 4 a 1 ) + 36 = 0 \Leftrightarrow 12a(4a-1)-12\sqrt{12a(4a-1)}+36=0 Let 12 a ( 4 a 1 ) = y 0 \sqrt{12a(4a-1)}=y\geq 0

y 2 12 y + 36 = 0 y = 6 \Rightarrow y^2-12y+36=0 \Rightarrow y=6 48 a 2 12 a = 36 a = 1 \Rightarrow 48a^2-12a=36 \Rightarrow a=1 a = 3 4 a=-\frac{3}{4} Because of a > 0 a> 0 So a = 1 a= 1 x = ± 1 \Rightarrow x=\pm 1 S = 1 1 = 0 S=1-1=0

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