3.4 Lösning 3c

${\color{White} x} \quad \underline{x_1 = 2} \,$:

$$f''(x) \, = \, 8\,x$$

$$f''(2) \, = \, 8\cdot 2 = 16 > 0 \quad \Longrightarrow \quad x_1 = 2 \quad {\rm lokalt\;minimum.}$$

${\color{White} x} \quad \underline{x_2 = -2} \,$:

$$f''(-2) \, = \, 8\cdot (-2) = -16 < 0 \quad \Longrightarrow \quad x_2 = -2 \quad {\rm lokalt\;maximum.}$$

$$f''(2) \neq 0 \quad {\rm och} \quad f''(-2) \neq 0 \quad \Longrightarrow \quad f(x) \, {\rm har\;inga\;terasspunkter.}$$