Question 8 - A-Level Maths

Given that \(\log _ { a } b = c\), express \(b\) in terms of \(a\) and \(c\).
By forming a quadratic equation, show that there is only one value of \(x\) which satisfies the equation \(2 \log _ { 2 } ( x + 7 ) - \log _ { 2 } ( x + 5 ) = 3\).