Noise pollution is any loud sound that is either harmful or annoying to humans and animals. Generally, noise is produced by household appliances, big trucks, vehicles and motorbikes on the road, as well as planes and helicopters flying over cities, and loudspeakers. Noise pollution can cause stress, illnesses, hearing loss, sleep loss, and lost productivity. Its health effects include anxiety, stress, headaches, irritability, and nervousness. Therefore, noise-producing industries, airports, and bus terminals should be located far from living areas. Moreover, officials should check the misuse of loudspeakers, outdoor parties, discos, and public announcement systems. By doing so, we can reduce noise pollution and protect people’s health

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mai thoát chết r cám ơn bn

em khum bít :)? cô nói ko lm thì chết

Em tách nhỏ ra để hỏi, không đăng cả đề như thế này, em nhé!

Ok bạn nhé

Ta có \(\dfrac{a^3}{a^2+b^2}=a-\dfrac{ab^2}{a^2+b^2}\ge a-\dfrac{ab^2}{2ab}=a-\dfrac{b}{2}=\dfrac{2a-b}{2}\)(áp dụng cosi cho \(a^2+b^2\ge2ab\))

\(\dfrac{b^3}{b^2+1}=b-\dfrac{b}{b^2+1}\ge b-\dfrac{b}{2b}=b-\dfrac{1}{2}=\dfrac{2b-1}{2}\)(áp dụng cosi cho\(b^2+1\ge2b\))

\(\dfrac{1}{a^2+1}=1-\dfrac{a^2}{a^2+1}\ge1-\dfrac{a^2}{2a}=1-\dfrac{a}{2}=\dfrac{2-a}{2}\)( áp dụng cosi cho \(a^2+1\ge2a\))

Cộng vế theo vế 

\(\dfrac{a^3}{a^2+b^2}+\dfrac{b^3}{b^2+1}+\dfrac{1}{a^2+1}\ge\dfrac{2a-b+2b-1+2-a}{2}\)\(\ge\dfrac{a+b+1}{2}\left(đpcm\right)\)

Dấu "=" xảy ra <=> a=b=1

Ta có:

\(36=2^2.3^2\)

\(54=2.3^3\)

\(ƯCLN\left(36;54\right)=2.3=6\)

\(BCNN\left(36;54\right)=2^2.3^3=4.27=108\)

ikyjt

10: \(\left(\sqrt{3-\sqrt{5}}+\sqrt{3+\sqrt{5}}\right)^2\)

\(=\left(\sqrt{3-\sqrt{5}}\right)^2+\left(\sqrt{3+\sqrt{5}}\right)^2+2\cdot\sqrt{\left(3-\sqrt{5}\right)\left(3+\sqrt{5}\right)}\)

\(=3-\sqrt{5}+3+\sqrt{5}+2\cdot\sqrt{9-5}\)

\(=6+2\cdot2=10\)

11: \(\left(\sqrt{\sqrt{7}+\sqrt{3}}+\sqrt{\sqrt{7}-\sqrt{3}}\right)^2\)

\(=\left(\sqrt{\sqrt{7}+\sqrt{3}}\right)^2+\left(\sqrt{\sqrt{7}-\sqrt{3}}\right)^2+2\cdot\sqrt{\left(\sqrt{7}+\sqrt{3}\right)\left(\sqrt{7}-\sqrt{3}\right)}\)

\(=\sqrt{7}+\sqrt{3}+\sqrt{7}-\sqrt{3}+2\cdot\sqrt{7-3}\)

\(=2\sqrt{7}+2\cdot2=2\sqrt{7}+4\)

12: \(\left(\sqrt{\sqrt{11}+\sqrt{7}}-\sqrt{\sqrt{11}-\sqrt{7}}\right)^2\)

\(=\left(\sqrt{\sqrt{11}+\sqrt{7}}\right)^2+\left(\sqrt{\sqrt{11}-\sqrt{7}}\right)^2-2\cdot\sqrt{\left(\sqrt{11}-\sqrt{7}\right)\left(\sqrt{11}+\sqrt{7}\right)}\)

\(=\sqrt{11}+\sqrt{7}+\sqrt{11}-\sqrt{7}-2\cdot\sqrt{11-7}\)

\(=2\sqrt{11}-4\)

13:

\(\sqrt{\sqrt{2}-1}\cdot\sqrt{2-\sqrt{3-\sqrt{2}}}\cdot\sqrt{2+\sqrt{3-\sqrt{2}}}\)

\(=\sqrt{\sqrt{2}-1}\cdot\sqrt{4-\left(3-\sqrt{2}\right)}\)

\(=\sqrt{\sqrt{2}-1}\cdot\sqrt{\sqrt{2}+1}\)

\(=\sqrt{2-1}=1\)

14:

\(\sqrt{4+\sqrt{8}}\cdot\sqrt{2+\sqrt{2+\sqrt{2}}}\cdot\sqrt{2-\sqrt{2+\sqrt{2}}}\)

\(=\sqrt{4+2\sqrt{2}}\cdot\sqrt{\left(2+\sqrt{2+\sqrt{2}}\right)\left(2-\sqrt{2+\sqrt{2}}\right)}\)

\(=\sqrt{4+2\sqrt{2}}\cdot\sqrt{4-2-\sqrt{2}}\)

\(=\sqrt{\left(4+2\sqrt{2}\right)\left(2-\sqrt{2}\right)}\)

\(=\sqrt{8-4\sqrt{2}+4\sqrt{2}-4}=\sqrt{4}=2\)

\(B=\dfrac{3}{1x2}+\dfrac{3}{2x3}+...+\dfrac{3}{50x51}\)

\(B=3x\left(\dfrac{1}{1x2}+\dfrac{1}{2x3}+...+\dfrac{1}{50x51}\right)\)

\(B=3x\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{50}-\dfrac{1}{51}\right)\)

\(B=3x\left(1-\dfrac{1}{51}\right)=3x\dfrac{50}{51}=\dfrac{150}{51}\)

CẢM ƠN BN