Arock is thrown in the air from the edge of a seaside cliff. its height in feet is represented by f(x) = –16(x^2 – 8x – 9), where x is the number of seconds since the rock was thrown. the height of the rock is 0 feet when it hits the water. how long does it take the rock to hit the water?

Since x is the number of seconds it took the rock to hit the water, x is the value that we are looking for. When the rock hits the water, it's height is 0, therefore, f(x) = 0. So, we can set the expression on the right equal to 0, and solve for 0. Let's do just that:


We can divide by -16, nothing will happen because 0 divided by anything is 0:


To factor any trinomial in standard form (given below), we must find two numbers that add to "b" and multiply to "c":


So, for this specific question, let's find two numbers that add to -8 and multiply to 9. These are clearly 9 and -1. We can write it in this way now:


Both answers would be valid, but there can't be negative time, so your answer is "It takes 9 seconds for the rock to reach the water."

56 ur welcome:

Answer: b 2 = 1.

step-by-step explanation: given equation a = h(b 1+b 2)

also we are given values of a, h and b 1 as :

a = 16, h = 4, and b 1 = 3.

in order to solve it for b 2, we need to plug the given values of   a, h and b 1 .

therefore, plugging values of   a, h and b 1   in given equation, we get

16 = 4( 3 + b 2)

first dividing both sides by 4, we get

4 = 3 + b 2

subtracting 3 from both sides, we get

4 -3 = 3 -3 + b 2

1 = b 2.

therefore, b 2= 1.