x^2 + 4√(2x^4) - x^3 + 9x^2 + 4

= x^2 +4*√2 * x^2 - x^3 + 9x^2 + 4

= - x^3  + 10x^2 + 4√2 x^2 + 4

= -x^3 + 2x^2( 5 + 2√2) + 4

54 km / hours

step-by-step explanation:

we need to convert seconds to hours

60 seconds = 1 minutes

60 minutes = 1hour

15 m         60 second   60 minutes

  * *         = 54000 meters/ hour

second     1 minute             1 hour

now we need to convert meters to km

1000 m = 1 km

54000 m       1 km

*   = 54 km / hours

hour               1000m