Chapter 4 - Exponential and Logarithmic Functions - Exercise Set 4.4 - Page 490: 85

Since $x \ne - 28$, $x = 28$

$2 \log x - \log 7 = \log 112$ $\log x^{2} - \log 7= \log 112$ $\log \frac{x^{2}}{7} = \log 112$ $\frac{x^{2}}{7} = 112$ $x^{2} = 784$ $x = ±\sqrt {784}$ $x = ±28$ Since $x \ne - 28$, $x = 28$