giải phương trình : a.(x^2+3x)^2+8(x^2+3x)

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Red Alert: Volcanoes Volcanoes can be fun to learn about. It can be neat to watch them erupt. But if you live near a volcano, you know that they are dangerous! An eruption can like an explosion. Rock and lava can throw up into the air. Streams of red hot lava quickly run down from the peak of the volcano. The air is filled with deadly gases. These things can put many lives in danger. Scientists have learned that there are many things that they can study to help them tell when an eruption might happen. They can study the movements of the ground. When a volcano is about to erupt, the ground will often move just like it does during an earthquake. Scientists can also measure the gases that come out of a volcano. Most volcanoes emit gases all of the time. More gases are let out as the volcano gets closer to erupting. They can also study the way the land and water around the volcano. Scientists can read these signs and warn people of danger. They may not realize it, but their work helps to keep people safe! 1. Read the passage and choose the best answer A, B,Cor D toeach question below. 1. In the passage, a volcanic eruption is compared as . A.an explosion B.an exploration C.a bomb D.a danger 2. can come out from a volcanic eruption. A. Rock B.Lava C.Gases D.All above 3. can study many things to predict when an eruption might happen. A.Economists B.Scientists C.People D.Biologists 4. There are ways for studying to estimate the time an eruption might happen. A. 1 B. 2 C. 3 D. 4 5. When an eruption is going to happen, . A.the ground moves as it does during an earthquake. B.the gases don't come out of it more than usual. C.only the water around it changes. D.the ground moves slowly and weakly.