Can somebody please please please help me solve this equeation, i have a

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Kylie.Carson_xox

New member
unit test coming up!!? I will be so grateful if you help me!!
the question is this

Ann Smith won a bronze medal in the woman's springboard competition. She somersaults from a 3m springboard. Her height, h (meters), above the water t seconds after she leaves the board is given by h=-4.9t^2+8.8t+3
How long is it until Smith reaches the water?

I know the answer is supposed to be 2.1s, but i have no clue how to get there, please show all your steps if you can help me!
 
ok assuming that the water is at h=0 so solve the equation when height is equal to zero:
0 = -4.9t^2 + 8.8t + 3
t = -0.293
t = 2.0889

which one makes sense?
 
You know her height at any given time(t) is expressed by that equation. So when she hits the water, her height is zero.

So, all you do is set h = 0.

0 = -4.9t^2 + 8.8t + 3
this is a quadratic equation, so either use the quadratic formula to find t(time), or you can graph it and find the x-intercept(where y = 0, where her height = 0)
 
Position function:

h(t) = - 4.9t² + 8.8t + 3

Ann will reach the water when h(t) = 0, so

- 4.9t² + 8.8t + 3 = 0

Using the Quadratic Equation where a = - 4.9, b = 8.8 and c = 3,

t { - 0.293, 2.089 }

Time can't run backwards, so

t = 2.089 sec.
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