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duchuy0405
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1.cho m<n chứng minh 4m-7<4n-7
2.a^2+b^2+c^2+3≥2(a+b+c)
3.a^2+b^2+1≥ab+a+b
4.a^2+1/4≥a
5.a^4+1≥a(a^2+1)
6.a^2+a+1/a^2-a+1>0
2.a^2+b^2+c^2+3≥2(a+b+c)
3.a^2+b^2+1≥ab+a+b
4.a^2+1/4≥a
5.a^4+1≥a(a^2+1)
6.a^2+a+1/a^2-a+1>0