Let's start from what we know.

Note that:

(sign of last term will be + when n is even and - when n is odd).
Sum is finite so we can split it into two sums, first

with only positive trems (squares of even numbers) and second

with negative (squares of odd numbers). So:

And now the proof.
1) n is even.
In this case, both

and

have

terms. For example if n=8 then:

Generally, there will be:

Now, calculate our sum:



So in this case we prove, that:

2) n is odd.
Here,

has more terms than

. For example if n=7 then:

So there is

terms in

,

terms in

and:

Now, we can calculate our sum:




We consider all possible n so we prove that:
Answer:
15/8
Step-by-step explanation:
Let "d" be the total distance, that is, the distance for swimming (s), running (r) and going by bike (b).
d = s + r + b [1]
1/24 of the total distance is covered by swimming.
s = 1/24 d [2]
1/3 of the distance is covered by running.
r = 1/3 d [3]
If we replace [2] and [3] in [1], we get
d = 1/24 d + 1/3 d + b
b = d - 1/24 d - 1/3 d
b = 24/24 d - 1/24 d - 8/24 d
b = 15/24 d = 5/8 d
The ratio of the distance covered by bike to the distance covered by running is:
b/r = (5/8 d)/(1/3 d) = 15/8
Answer:
x y
7 4
2 3
7 5
Step-by-step explanation:
it cant be a function if it has two of the same domains.