# Math

A ball is thrown straight up from a bridge over a river and falls into the water. The height, h, in meters, of the ball above the water t seconds after being thrown is approximately modeled by the relation h=-5t^2+10t+35.

a) What is the maximum height of the ball above the water? (1 mark)

b) How long does it take for the ball to reach the maximum height? (1 mark)
See below for what I need for the answer to be valid

c) After how many seconds does the ball hit the water? (1 mark)
I need help with this question with an actual explanation of you got the answer as I can't seem to figure it out.

d) How high is the bridge above the river? (1 mark)

The height of the bridge above the water would be 35 meters

h=-5t^2+10t+35
h=-5(0)^2+10(0)+35
h=0+0+35
h=35

1. 👍 0
2. 👎 0
3. 👁 334
1. (b) t = -b/2a = 10/10 = 1
(a) find h(1)
(c) solve for t when h=0
-5t^2+10t+35 = 0
or,
t^2-2t-7 = 0
t = (2±√30)/2 (use quadratic formula)
(d) correct

1. 👍 0
2. 👎 0
2. oops. That's

(2±√32)/2 = 1±√8

1. 👍 0
2. 👎 0

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