Find value or $W=\sqrt[4x+4]{3^{x}\left ( \sqrt{5}-1 \right )}$ according to condition $9^{x}=6^x +4^x$

55 Views Asked by At

If $$9^{x}=6^x +4^x$$

Find the value of:

$$W=\sqrt[4x+4]{3^{x}\left ( \sqrt{5}-1 \right )}$$

Solving the equation arrives at:

$x = \frac{\log\left ( \sqrt{5}-1 \right ) - \log(2)}{\log(2) - \log(3)}$

But W yields a giant result, Is there any algebraic manipulation that I do not see

1

There are 1 best solutions below

1
On BEST ANSWER

Note that $$1=\left(\frac23\right)^x+\left(\frac49\right)^x$$ Let $a=\left(\frac23\right)^x$ $$a^2+a-1=0$$ Solving gives $$a=\left(\frac{\sqrt5 -1}{2}\right)$$ $$\left(\frac23\right)^x=\frac{\sqrt5 -1}{2}$$ $$\left(\frac32\right)^x=\frac{2}{\sqrt5-1}$$ $$3^x=\frac{2^{x+1}}{\sqrt5-1}$$

Substitute for this in question $$\left(\left(\frac{2^{x+1}}{\sqrt5-1}\right)(\sqrt5-1)\right)^{\frac{1}{4(x+1)}}=2^{\frac{x+1}{4(x+1)}}=2^{1/4}$$