\(VT=2sin^6x-3cos^4x+1=2sin^6x+2cos^6x-3cos^4x-3sin^4x+1+3sin^4x-2cos^6x\)
Dài quá, không đủ viết chung 1 dòng, tách lẻ ra:
\(2\left(sin^6x+cos^6x\right)=2\left[\left(sin^2x+cos^2x\right)^3-3sin^2x.cos^2x\left(sin^2x+cos^2x\right)\right]\)
\(=2-6sin^2x.cos^2x\)
\(-3\left(sin^4x+cos^4x\right)=-3\left(sin^2x+cos^2x\right)^2+6sin^2x.cos^2x\)
\(=-3+6sin^2x.cos^2x\)
\(\Rightarrow VT=2-6sin^2x.cos^2x-3+6sin^2x.cos^2x+1+3sin^4x-2cos^6x\)
\(=3sin^4x-2cos^6x\)
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