An object is moving along the$$x$-$axis. $$It$\text{'}$s position at any time$$t is given by the function$$x$($t$)=8\mathrm{.}6$t$2+5\mathrm{.}5$t $+5\mathrm{.}9.$Find the instantaneous velocity of the particle at$$t $=-2\mathrm{.}69.$Round your answer to two decimal places.