V vectorspace, $\tau: V \rightarrow V$, $\tau$ $\mathbb{K}$-linear and bijective. Proof $\tau^{-1}: V \rightarrow V$
So basically $\tau$ takes an inputvector of V and maps it onto an outputvector in the same vectorspace. Now, intuitively $\tau^{-1}$ will an inputvector of V and map it back into the same Vectorspace.
In my attempt, I try to proof $\tau^{-1}$ is $\mathbb{K}$- linear:
$\tau(\lambda u) = \alpha w$
$\tau(\mu v) = \beta x$,
$\tau^{-1}(\alpha w) = \lambda u$
$\tau^{-1}(\beta x) =\mu v$
$\tau^{-1}(\alpha w) + \tau^{-1}(\beta x) = \lambda u + \mu v \Leftrightarrow$
$\alpha + \beta x = \tau(\lambda u) + \tau (\mu v) \Leftrightarrow$
$\alpha w + \beta x = \tau(\lambda u + \mu v) \Leftrightarrow$
$\tau^{-1}(\alpha w+ \beta x) = \lambda u + \mu v$
So all in all: $\tau^{-1}(\alpha w) + \tau^{-1}(\beta x) = \lambda u + \mu v = \tau^{-1}(\alpha w+ \beta x) \Rightarrow \tau^{-1}(\alpha w) + \tau^{-1}(\beta x) = \tau^{-1}(\alpha w+ \beta x)$