Answer:
Step-by-step explanation:
Using brackets will really help.
y = (x^2 + 4x + ... ) - 5 You are trying to complete the square. The square in this case is a trinomial that is squared.
To do that, you take 1/2 the linear term (4x)/2, drop the x (4/2), and square the result (4/2)^2. The number is 2^2 which is 4.
So far what you have is
y = (x^2 + 4x + 4) - 5
Now you just can't add 4 without adjusting it somehow. If you do, the whole question will change it's value. Because you added 4 inside the brackets, you must subtract 4 outside the brackets.
What that means is 4 inside - 4 outside. So it looks like this
y = (x^2 + 4x + 4) - 5 - 4
Now you continue on
y = (x + 2)^2 - 9 The 4 combines with the 5 to make nine.
Answer: 2.28%
Step-by-step explanation:
Given: An airport find that at the present time, the mean noise level is 103 decibels and the standard deviation is 5.4 decibels.
The distribution of noise levels(x) for all jets during takeoff over the neighborhood has a normal distribution.
The probability that jets have a noise level less than 92.2 decibels when taking off over this neighborhood will be :-
Hence, the percent of these jets have a noise level less than 92.2 decibels when taking off over this neighborhood = 2.28%
