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下列物质中属于光源的是: [ ] A、太阳灶的反光镜 B、月亮 C、蜡烛的火焰 D、电镀的小刀
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It’s time to say goodbye to my school. I’ll always remember the people _______ have helped me.
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若bn=2(1-n)an(n≥2),求证:b22+b32+…+bn2<1.
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