Question

Rui is a professional deep water free diver.

Answer 1

Answer:

10 took khan

Step-by-step explanation:

Answer 2

Answer:

Rui will reach his lowest altitude after diving for 10 seconds

Step-by-step explanation:

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

• h = $\frac{-b}{2a}$ and k = y at x = h

In the given question

∵ d(x) = $\frac{1}{2}$ x² - 10 x

∵ d represents his altitude in meters after x seconds

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

∴ a =  $\frac{1}{2}$ and b = -10

∵ h = $\frac{-b}{2a}$

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

∴ h = $\frac{--10}{2.\frac{1}{2}}$ = 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