1 Let \(a\) be a positive constant.
(a) Sketch the curve with equation \(y=\frac{a x}{x+7}\).

(b) Sketch the curve with equation \(y=\left|\frac{a x}{x+7}\right|\) and find the set of values of \(x\) for which \(\left|\frac{a x}{x+7}\right|>\frac{a}{2}\).