Solve the following quadratic equation :

Comparing x² + 4x - 8 = 0 with ax² + bx + c, we get :

a = 1, b = 4 and c = -8.

By formula,

$$\begin{aligned}\Rightarrow x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \\[1em] = \frac{-4 \pm \sqrt{4^2 - 4 \times 1 \times (-8)}}{2 \times 1} \\[1em] = \frac{-4 \pm \sqrt{16 + 32}}{2} \\[1em] = \frac{-4 \pm \sqrt{48}}{2} \\[1em] = \frac{-4 \pm 4\sqrt{3}}{2} \\[1em] = -2 \pm 2\sqrt{3} \\[1em] = -2 \pm 2 \times 1.732 \\[1em] = -2 \pm 3.464 \\[1em] = -2 + 3.464 \text{ or } -2 - 3.464 \\[1em] = 1.464 \text{ or } -5.464 \\[1em] = 1.5 \text{ or } -5.5\end{aligned}$$

Hence, x = 1.5 or 5.5