Consider the parametric curve:

$x=64-t^2$

$y=t^3-9t$

At which $t$ value$($s$)$ is the tangent to this curve vertical? $($ Note: If there is more than one write them as a comma separated list$)$

$t=$

$$

Write the point$($s$)$ at which the tangent is vertical. $($ Note: If there is more than one write them as a comma separated list, e$.$g$.(1,2),(3,4)$

At which $t$ value$($s$)$ is the tangent to this curve horizontal? $($Note: If there is more than one write them as a comma separated list$).$

$t=$