A)
well, we know the elevator's rate is -20 f/s, ok, so every second, is dropping 20 feet, therefore, "y" is "distance from the ground floor", so when y = 0, meaning the distance to the ground floor is 0, so you ARE at the ground floor then.
and "x" is how many seconds you've been in the elevator.
now, she got in the elevator for 6 seconds, so, the elevator went down by 20 * 6, or 120 feet down, reason why the slope is negative, when she stopped, she was 350 feet away from the ground floor still though.
if the elevator went down 120 feet, and she's still 350 feet from the ground floor, that means she boarded the elevator at 120 + 350 feet, or 470 feet.
b)
Answer:
First, a rational number is defined as the quotient between two integer numbers, such that:
N = a/b
where a and b are integers.
Now, the axiom that we need to use is:
"The integers are closed under the multiplication".
this says that if we have two integers, x and y, their product is also an integer:
if x, y ∈ Z ⇒ x*y ∈ Z
So, if now we have two rational numbers:
a/b and c/d
where a, b, c, and d ∈ Z
then the product of those two can be written as:
(a/b)*(c/d) = (a*c)/(b*d)
And by the previous axiom, we know that a*c is an integer and b*d is also an integer, then:
(a*c)/(b*d)
is the quotient between two integers, then this is a rational number.
The answer is......... 27
1 is not even yet it is a factor of 8. Alice is wrong.