The foci of the hyperbola with equation 5y^2-4x^2=20 will be given as follows:
divide each term by 20
(5y^2)/20-(4x^2)/20=20/20
simplifying gives us:
y^2/4-x^2/5=1
This follows the standard form of the hyperbola
(y-k)²/a²-(x-h)²/b²=1
thus
a=2, b=√5 , k=0, h=0
Next we find c, the distance from the center to a focus.
√(a²+b²)
=√(2²+(√5)²)
=√(4+5)
=√9
=3
the focus of the hyperbola is found using formula:
(h.h+k)
substituting our values we get:
(0,3)
The second focus of the hyperbola can be found by subtracting c from k
(h,k-c)
substituting our values we obtain:
(0,-3)
Thus we have two foci
(0,3) and (0,-3)
Answer:
There are total 30 books in the 5 feet high stack of books.
Step-by-step explanation:
The complete question is
Given, Each note book is 2 inches thick, How many notebooks do you think it would take to make a stack that is 5 feet high
Solution
Thickness of each book 
The total height of the book stack is
feet.
The number of books in the stack is equal to total height of the stack divided by the thickness of one book
Number of books in five feet high stack is

Hence, there are total 30 books in the 5 feet high stack of books.
Since 25% is smack in the middle between 20% and 30%, it will take equal volumes of ech to make a 25% solution.
Since 4 gallons of 30% solution was used, so 4 gallons of 20% solution will be needed.
The answer to your question is b
Answer:
Here it is. The table is on the first one at the bottom.
Step-by-step explanation: