寫出與使用不等式 3 (英)
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- A popular R&B band recently returned from a successful
- three-city tour where they played to at
- least 120,000 people.
- My brain immediately says that's greater than or equal
- to 120,000.
- If they had an audience of 45,000 in Mesa and another
- 33,000 in Denver, how many people attended
- their show in Las Vegas?
- So let's say Las Vegas, I'll just use l for Las Vegas.
- So the number of people who attended their show in Las
- Vegas plus the number that attended their show in Mesa,
- which is 45,000, plus the number of people that attended
- their show in Denver, which is 33,000-- those are three
- cities right there, Las Vegas, Mesa, and Denver-- that has to
- be at least 120,000 people.
- Or another way of interpreting that is greater than or equal
- to 120,000.
- So to figure out how many people attended their show in
- Las Vegas, we just solve for l on this inequalty.
- So if we simplify this left-hand side, we get the
- number of people in Las Vegas plus-- what's 45,000 plus
- 33,000, that is 78,000-- 78,000 is going to be greater
- than or equal to 120,000.
- Now to isolate the l on the left-hand side of the
- inequality, we can subtract 78,000 from both sides.
- So minus 78,000, minus 78,000 on the left-hand side, these
- cancel out.
- And we're just left with the number of people who attended
- the show in Las Vegas is going to be greater than or equal to
- 120,000 minus 78,000.
- So 120,000 minus 80,000 is 40,000, and it's going to be
- another 2,000.
- So the number of people who attended Las Vegas is going to
- be greater than or equal to 42,000 people.
- And we're done, that's it
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