Answer:
Step-by-step explanation:
Let x and y are the two positive real numbers
product of two numbers is 21
The sum of the two numbers is f(x) =x+y
Replace y with 21/x
we need to find smallest possible sum , so we take derivative using power rule
when sum is minimum then the derivative is equal to 0
multiply both sides by x^2
Take square root on both sides
Answer: yes, it is
Step-by-step explanation:
A number is divisible by 6 if it is divisible by 2 and 3 simultaniously.
n = k(k+1)(k-1)
If k-1 is a multiple of 3, n is divisible by 3, so one of the requirements is ok.
Now, if k-1 is a multiple of 3, it can be even or odd.
if k-1 is even, then it is divisible by 2 and as it is divisible by 3 as well, n is divisible by 6
if k-1 is odd, then k and k+1 is even, hence, divisible by 2.
As n = k(k+1)(k-1), n is also divisible by 6.
speed of plane flying east = x
speed of plane flying west = x+75
total speed = 2x+75
distance after 4 hours ( 7-3) = 8x+300
8x+300 = 5460
8x = 5160
x = 5160/8 = 645
speed of plane flying east = 645 km/h
69.9 is exactly 3 standard deviations away, which means that 78.9 is +3 (more than 3) standard deviations
So the answer is 78.9
