1a) Time = Distance/Speed
t= 20/x seconds
b) d=25m
s= x+0.5 m/s
t= d/s = 25/x+0.5
c) total time = 6 seconds
therefore, 20/x + 25/x+0.5 = 6
make a common denominator of x(x+0.5):
(20(x+0.5) + 25x)/x(x+0.5) = 6
move the demoninator to the other side, and expand to form:
20x+10+25x = 6x(x+0.5)
45x+10= 6x^2 +3x
tidying it up (moving everything to one side)
6x^2 - 42x-10 = 0
divide everything by 2
3x^2-21x-5= 0 (as required)
d) use quadratic formula to solve
e) therefore, what does x equal?
hope this helps
