One number exceeds another by 8. The sum of the numbers is 46. What are the numbers?
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<h3>Answer: (-infinity, 7]</h3>
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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.
Multiply the equation:
The solution set is the same, because multiplying both sides of an equation by a non-zero number doesn't change the solution set. In fact, if you rewrite the equation as
Multiplying this by 3 (or whatever number, for all it matters) gives
Now, a product is zero if and only if at least one of the factor is zero. So, either or
Since the first is clearly impossible, the second one must be true, which is the original equation.