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phanthiencbt


[tex]\frac{a(sin)^4x}{c(sin)^2x+d(cos)^2y}+\frac{a(cos)^4x}{c(cos)^2x+d(sin)^2y}\leq\frac{a(sin)^4x}{c(sin)^2x}+\frac{a(cos)^4x}{c(cos)^2x}[/tex]
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