Answer:
3 hours
Step-by-step explanation:
The difference between the initial temperature and the temperature after an hour is an increase of 5 degrees. Since we need to calculate the time it would take for the temperature to rise to 60 degrees we need to find the difference in degrees from the current temperature to 60 degrees.
60 - 45 = 15 degrees
Since 1 hour equals an increase of 5 degrees we need to divide 15 by 5 to calculate how many hours before the temperature increases to 60 degrees
15 / 5 = 3 hours
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."
Answer:
9/20, or 0.45 mile.
Step-by-step explanation:
To find the area of a rectangle, multiply length times width. In this problem we are given both the length and width.
×
is just 9/20, which is 0.45.
Answer:
The answer is approximately 5.09 seconds.
Step-by-step explanation:
The given equation is:
f(x) = -5x^2 + 250
To find the elapsed time, x, set the equation equal to 120 and solve for x:
-5x^2 + 250 = 120
-5x^2 = -130
x^2 = -130/-5 = 26
x = Sqrt(26) = 5.09 seconds.