Khánh Đan
2 phút trước

Ta có: \(-x^2+4x+3=-\left(x^2-4x+4\right)+7=-\left(x-2\right)^2+7\le7\forall x\in R\)

⇒ max y = 7 tại x = 2

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Trúc Giang
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Quang Anh

XI. Read the passage carefully, then do the tasks.
Scientists say it could take at least 1,500 years before humans make contact with
species of aliens, or for them to communicate with or find us. Astronomers from Cornell
University in the USA combined two existing theories about the possibility of life existing on
other planets to form a new equation. One of these theories is the Fermi Paradox described
by physicist Enrico Fermi in 1950. This States that while billlons of Earth-like planets exist
in our galaxy, not One has made contact with Earth yet. The other is the principle, which
suggests that because there is life on Earth, it will typically exist on Earth-like planets
throughout the universe.
“We haven’t heard from aliens yet, as space is a big place, but that doesn’t mean no
one is out there,” study author and Cornell astronomy student Evan Solomonides said.
According to Solomonides, extraterrestrials could have received signals from Earth.
However, he suggests that ET would not have been able to decode them. He said they would
need to decode the light waves into sounds and analyse 3,000 human languages to
understand any messages. He said that signals from Earth have only reached about 8,500
stars and that the Milky Way galaxy alone contains 200 billion stars. He added: “If we stop
listening or looking, we may miss the signals, so we should keep looking.”
A. Decide whether the following statements are true (T) or false (F).
1. Scientists say humans are unlikely to hear from aliens for at least 1,500 years.
2. Cornell astronomers examined 20 different theories on whether aliens exist.
3. One theory that was looked at was from a physicist.
4. Another theory said there is life on Earth so there will be on other planets.
5. Solomonides said aliens couldn’t receive signals from Earth as space is a big place.
6. He said aliens would need to decode 3,000 languages to understand human message.
7. So far Earth’s broadcast signals have reached around 8,500 stars.
8. The researcher suggested we stop looking for alien life
 mọi người ơi giúp mik vs mik cảm ơn rất nhiều


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