-6 is greater than 5 is wrong
0=40-10t-5t^2
t^2+2t-8=0
(t+4)(t-2)=0
t=-4 (not a solution) or t=2
Answer: after 2 seconds
Why not look up "standard deviation" yourself, to be sure? But yes, the std. dev. is the sqrt of the variance.
The equation is 2.5(m)+3
<span>Since the ride only costs $3, and for every mile, $2.5 will be charged.</span>
