Question 720636


Time = distance /speed

original speed = x

{{{450/x +450/(x+15)= (900/x)- 3/2}}}


{{{450/(x+15)-450/x =-3/2}}}


450x-450(x+15) = (-3/2) ( x*(x+15)


-6750=(-3/2)(x^2+15x)

-13000=-3x^2-45x

3x^2+45x-13500=0

/3

x^2+15x-4500=0

x^2+75x-60-4500-0

(x+75)(x-60)=0

x= 60 km/h the original speed