Question 1159133
the height of the platform is the constant 40 m.
the landing point is found by taking the positive root of -5t^2+10t+40=0
or t^2-2t-8=0
(t-4)(t+2)=0
t= 4 seconds

{{{graph(300,300,-5,5,-20,60,-5x^2+10x+40)}}}