Solve: $\rm \frac{2^{x+1}}{16} + \frac{16}{2^{x+1}} = \frac{65}{8}$
Solution
Given
$\rm \frac{2^{x+1}}{16} + \frac{16}{2^{x + 1}} = \frac{65}{8}$
$\rm or, \frac{2^{x+1}}{16} + \left ( \frac{2^{x+1}}{16} \right )^{-1} = \frac{65}{8}$
Let $\rm a = \frac{2^{x + 1}}{16}$, we get,
$\rm or, a + a^{-1} = \frac{65}{8}$
\[\rm a + \frac{1}{a} = \frac{65}{8}\]
Multiplying both sides by \(\rm a\), we get:
\[\rm a^2 + 1 = \frac{65a}{8}\]
Multiplying both sides by \(\rm 8\), we get:
\[\rm 8a^2 + 8 = 65a\]
Rearranging terms, we have a quadratic equation in \(\rm a\):
\[\rm 8a^2 - 65a + 8 = 0\]
The above equation is quadratic in a. We use the mid-term factorization formula to solve the equation.
$\rm or, 8a^{2} - (64 + 1) a + 8 = 0$
$\rm or, 8a^{2} - 64a - a + 8 = 0$
$\rm or, 8a (a - 8) - 1 (a - 8) = 0$
$\rm or, (8a - 1)(a - 8) = 0$
Either
$\rm (8a - 1) = 0$
$\rm or, 8a = 1$
$\rm or, a = \frac{1}{8}$
Substitute $\rm a = \frac{2^{x + 1}}{16}$ into the equation, we get,
$\rm or, \frac{2^{x + 1}}{16} = \frac{1}{8}$
$\rm or, 2^{x + 1} = 2$
$\rm or, 2^{x + 1} = 2^{1}$
$\rm or, x + 1 = 1$
$\rm or, x = 1 - 1$
$\rm \therefore x = 0$
Or
$\rm (a - 8) = 0$
$\rm or, a = 8$
Substitute $\rm a = \frac{2^{x + 1}}{16}$ into the equation, we get,
$\rm or, \frac{2^{x + 1}}{16} = 8$
$\rm or, 2^{x + 1} = 16 \cdot 8$
$\rm or, 2^{x + 1} = 2^{4} \cdot 2^{3}$
$\rm or, 2^{x + 1} = 2^{4 + 3}$
$\rm or, 2^{x + 1} = 2^{7}$
$\rm or, x + 1 = 7$
$\rm or, x = 7 -1 $
$\rm \therefore x = 6$
Hence, the required values of x are x = {0, 6}.