Logging around!

Algebra Level 4

Find the product of the roots to the equation ( 6 × 9 1 x ) ( 13 × 6 1 x ) + ( 6 × 4 1 x ) = 0 \large \left ( 6\times{9^{\frac {1}{x}}} \right )-\left ( 13\times{6^{\frac {1}{x}}} \right ) +\left ( 6\times{4^{\frac {1}{x}}} \right )= 0


The answer is -1.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Sujoy Roy
Mar 8, 2015

Put a = 3 1 x a=3^{\frac{1}{x}} and b = 2 1 x b=2^{\frac{1}{x}} , in the given equation we get,

6 a 2 13 a b + 6 b 2 = 0 6a^2-13ab+6b^2=0 or, ( 2 a 3 b ) ( 3 a 2 b ) = 0 (2a-3b)(3a-2b)=0 .

So, a b = 3 2 1 x = 3 2 o r 2 3 \frac{a}{b}=\frac{3}{2}^\frac{1}{x}=\frac{3}{2}\: or\: \frac{2}{3} .

Thus, x = 1 , 1 x=1,-1 and product of the roots is 1 {-1} .

I've tried with x=1 and it satisfied the equation but why my answer is wrong?

Sarono Handoyo - 5 years, 9 months ago
Daniel Ferreira
Mar 8, 2015

6 ( 3 2 ) 1 x 13 ( 2 3 ) 1 x + 6 ( 2 2 ) 1 x = 0 6 \cdot (3^2)^{\frac{1}{x}} - 13 \cdot (2 \cdot 3)^{\frac{1}{x}} + 6 \cdot (2^2)^{\frac{1}{x}} = 0

Consideremos 3 1 x = m 3^{\frac{1}{x}} = m e 2 1 x = n 2^{\frac{1}{x}}= n .

Segue,

6 m 2 13 n m + 6 n 2 = 0 6 m 2 9 m n 4 m n + 6 n 2 = 0 3 m ( 2 m 3 n ) 2 n ( 2 m 3 n ) = 0 ( 3 m 2 n ) ( 2 m 3 n ) = 0 6m^2 - 13nm + 6n^2 = 0 \\\\ 6m^2 - 9mn - 4mn + 6n^2 = 0 \\\\ 3m(2m - 3n) - 2n(2m - 3n) = 0 \\\\ (3m - 2n)(2m - 3n) = 0

Fator I,

3 m 2 n = 0 3 m = 2 n 3 3 1 x = 2 2 1 x ( 3 2 ) 1 x = 2 3 ( 3 2 ) 1 x = ( 3 2 ) 1 1 x = 1 x = 1 3m - 2n = 0 \\\\ 3m = 2n \\\\ 3 \cdot 3^{\frac{1}{x}} = 2 \cdot 2^{\frac{1}{x}} \\\\ (\frac{3}{2})^{\frac{1}{x}} = \frac{2}{3} \\\\ (\frac{3}{2})^{\frac{1}{x}} = (\frac{3}{2})^{- 1} \\\\ \frac{1}{x} = - 1 \\\\ \boxed{x = - 1}

Fator II,

2 m 3 n = 0 2 m = 3 n 2 3 1 x = 3 2 1 x ( 3 2 ) 1 x = 3 2 1 x = 1 x = 1 2m - 3n = 0 \\\\ 2m = 3n \\\\ 2 \cdot 3^{\frac{1}{x}} = 3 \cdot 2^{\frac{1}{x}} \\\\ (\frac{3}{2})^{\frac{1}{x}} = \frac{3}{2} \\\\ \frac{1}{x} = 1 \\\\ \boxed{x = 1}

Com efeito,

x 1 x 2 = 1 \boxed{\boxed{x_1 \cdot x_2 = - 1}}

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...