Question 15****+Find \(k\) if \(\int k^x\,dx=\frac{k^x}{\ln 3}+C\) for all \(x\), with \(k>0\) and \(k\ne1\).
Question 16****+Choose a substitution type from the standard trigonometric substitution table for \(\sqrt{9-x^2}\).
Question 17****+Choose a substitution type from the standard trigonometric substitution table for \(\sqrt{x^2-16}\).
Question 18*****A student writes \(\int \frac1x\,dx=\frac{1}{2}x^2+C\). Explain the mistake and give the correct standard integral.
Question 20*****Explain why \(\int \frac{1}{|x|\sqrt{x^2-1}}\,dx=\operatorname{arcsec}|x|+C\) requires a domain restriction.