Use the rule y = -x + 7 to fill in the blank. If (-1, y) is on the graph, then y = ___
1 answer:
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<h3>Answer: 28</h3>
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Explanation:
Method 1
Imagine a table with 8 rows and 8 columns to represent all possible match-ups. You can actually draw out this table or just think of it as a thought experiment.
There are 8*8 = 64 entries in the table. Along the northwest diagonal, we have each team pair up with itself. This is of course silly and impossible. We cross off this entire diagonal so we drop to 64-8 = 56 entries.
Then notice that the lower left corner is a mirror copy of the upper right corner. A match-up like AB is the same as BA. So we must divide by 2 to get 56/2 = 28 different matches.
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Method 2
There are 8 selections for the first slot, and 8-1 = 7 selections for the second slot. We have 8*7 = 56 permutations and 56/2 = 28 combinations.
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Method 3
Use the nCr combination formula with n = 8 and r = 2
There are 28 combinations possible. Order doesn't matter (eg: match-up AB is the same as match-up BA).
Notice how the (8*7)/2 expression is part of the steps shown above in the nCr formula.
The rule for the sequence is S(n) = 2S(n-1) - S(n-2)
Alternative form: S(n) = S(n-1) + 3
Step-by-step explanation:
In this problem, we know the first two terms of the sequence:
S(1) = 2
S(2) = 5
We are told that each term after the second is created by subtracting the term before the previous term from twice the previous term. In other words, if we call:
S(n) the current term
S(n-1) the previous term
S(n-2) the term before the previous term
This statement translates into the following sequence:
S(n) = 2S(n-1) - S(n-2)
Because we are subtracting the term before the previous term, S(n-2), from twice the previous term, 2S(n-1).
We can apply now the rule to find the first few terms of the sequence after S(1) and S(2):
We notice also that each term of the sequence is just equal to the previous term plus 3, so the sequence can also be written as
S(n) = S(n-1) + 3
Learn more about sequences:
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