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

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

In the given question

∵ d(x) = x² - 10 x

∵ d represents his altitude in meters after x seconds

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

∴ a =   and b = -10

∵ h =

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

∴ h = = 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

the answer is 15% decrease

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