Question 315040
{{{ h=48t-16t^2=20}}}
{{{16t^2-48t+20=0}}}
{{{4t^2-12t+5=0}}}
Factor the quadratic.
{{{ (2t-5)(2t-1)=0 }}}
Two solutions:
{{{2t-5=0}}}
{{{2t=5}}}
{{{t=5/2}}}
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{{{2t-1=0}}}
{{{2t=1}}}
{{{t=1/2}}}
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The rocket first reaches 20 ft in 1/2 sec going up and then reaches 20 ft in 5/2 sec going down.