SOLUTION
From the question, we are told that y varies inversely as x
This is mathematically written as
Now, we will remove the proportionality sign and replace it with equal to sign =
If we do this, we will intoduce a constant k
So we have the formula
We will substitute the values of x for 10 and y for 8 into the formula to get k, we have
Now, we will substitute k for 80 back into the formula to get the inverse function, we have
Hence the answer is option C
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Explanation:
The first interval (-infinity, 3) describes any number less than 3, so we can write x < 3 in short hand (where x is the unknown number).
The second interval (-1, 7] means we start at -1 and stop at 7. We do not include -1 but include 7. So we say that (ie x is between -1 and 7; exclude -1, include 7)
If you were to graph each ona number line, you would see that the too intervals have overlapping parts. The right most edge extends out as far as x = 7. There is no left most edge as it goes onforever that direction.
Therefore, the to intervals combine to get which turns into the interval notation answer of (-infinity, 7]
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It might help to think of it like this: x < 3 and say "x is some number that is less than 3, or it is between -1 and 7". So x could be anything less than 7, including 7 itself.