Question 144268
Given {{{ d=0.044s^2 +1.1s }}}

What speed will result in a stopping distance of 80 feet?
{{{ 80 = 0.044s^2 +1.1s }}}
{{{ 0 = 0.044s^2 +1.1s - 80 }}}

use the quadratic equation with a = 0.044, b=1.1 and c=-80
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
You'll get two answers. One is negative, so that one is not an option. The other is 31.93mph.

Does that seem reasonable. Sho' nuf