$f\left(3\right)=23$

$f\left(x\right)=8$ gives you $x=0$ V $x=\pm 2$

Own answer.

Yes.

No, the answer to b) is such an example.

For every value of $a$ there is exactly one value of $K$.

$K\left(100\right)=67$

$K\left(a\right)=42+0.25a$

$1832$ m³

$(\pm 10,0)$ and vertex $(0,100)$

Do it.

$(-7.07;50)$ and $(7.07;50)$

for $y_1$: $(0,0)$ and $(\pm 2,0)$
for $y_2$: $(0,0)$ and $(4,0)$

Do it.

$(0,0)$ and $(2.3;3.9)$

$(0,0)$ and $(100,0)$

$(0,0)$ and $(50,0)$

$(-30,0)$ and $(50,0)$ with vertex $(10,-1600)$

$(-125,0)$