Question

Rui is a professional deep water free diver.

His altitude (in meters relative to sea level), X seconds after diving, is modeled by:
1
d(x)
2
22
10x
How many seconds after diving will Rui reach his lowest altitude?
seconds

Answer 1

10 took khan

Explanation:

Answer 2

Rui will reach his lowest altitude after diving for 10 seconds

Explanation:

In the quadratic equation y = ax² + bx + c, the coordinates of the lowest or the highest point is (h, k), where

• h =
  `(-b)/(2a)` and k = y at x = h

In the given question

∵ d(x) =
`(1)/(2)` x² - 10 x

∵ d represents his altitude in meters after x seconds

→ Compare it with the form above to find a and b

∴ a =
`(1)/(2)` and b = -10

∵ h =
`(-b)/(2a)`

→ Substitute the values of a and b in the rule to find h

∴ h =
`(--10)/(2.(1)/(2))` = 10

∴ h = 10

∵ h is the x-coordinate of the lowest point

∴ The time of the lowest altitude is 10 seconds

∴ Rui will reach his lowest altitude after diving for 10 seconds