So far we have considered quadratic expressions with no $x^1$ term. In this video we show how to handle expressions like $\sqrt{x^2 + 4x - 5}$ or $x^2 + 2x + 5$.
This means that any quadratic polynomial $x^2 +bx +c$ can be converted to a sum or difference of squares:$$x^2+bx+c= \left(x + \frac{b}{2}\right)^2 + \left ( c-\frac{b^2}{4}\right ) = \left(x + \frac{b}{2}\right)^2\pm a^2,$$depending on whether $c- b^2/4$ is positive or negative (we have set $|c-b^2/4|=a^2$). We then use our usual trig substitutions by setting $x+\frac{b}{2} = a \tan(\theta)$, or $a \sin(\theta)$, or $a \sec(\theta)$.
In the video, we apply this technique to three examples.