D and E are points on sides AB and AC respectively of triangle ABC such that DE || BC. If AD = x-1, DB = x – 3, AE = x + 3 and EC = x , the value of x is: ​

9514 1404 393

  9

Step-by-step explanation:

The triangles are similar, so corresponding sides are proportional.

  AE/AD = EC/DB

  (x+3)/(x -1) = x/(x -3)

  x^2 -9 = x^2 -x . . . . . . . cross multiply

  x = 9 . . . . . . . . . . . add x+9-x^2 to both sides

since the airplane is moving with constant speed then the distance travelled can be calculated by x=u*t

in km/h would be:

x=640*3.5=2.240 km

in m/s would be:

u=640 km/h= 640.000 m/h =640.000/ 3600 m/s =177.8 m/s

t= 3.5 h= 3.5 * 3600 s=12.600 s

then x=u*t= 177.8*12.600= 2.240.280 m

you didn't give me the choices, so i will just give you the graph so you can look at your choices and choose the right one.