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a/ \(\frac{-25}{\left(-x+2\right)\left(-3x-2\right)}< 0\Leftrightarrow\left[{}\begin{matrix}x< -\frac{2}{3}\\x>2\end{matrix}\right.\)
b/ \(\frac{1}{x-1}-\frac{2}{2x-1}>0\Leftrightarrow\frac{1}{\left(x-1\right)\left(2x-1\right)}>0\Rightarrow\left[{}\begin{matrix}x>1\\x< \frac{1}{2}\end{matrix}\right.\)
c/ \(\frac{2}{3-x}+\frac{2}{x-3}\le0\Leftrightarrow0\le0\) (luôn đúng)
Vậy nghiệm của BPT là \(R\backslash\left\{3\right\}\)
d/ \(1-\frac{x-1}{x^2-3x+2}\ge\Leftrightarrow\frac{x^2-4x+3}{\left(x-1\right)\left(x-2\right)}\ge0\Leftrightarrow\frac{\left(x-1\right)\left(x-3\right)}{\left(x-1\right)\left(x-2\right)}\ge0\)
\(\Rightarrow\left[{}\begin{matrix}x\ge3\\1< x< 2\\x< 1\end{matrix}\right.\)
e/ \(\frac{x+1}{x^2+x+2}-\frac{1}{x+1}>0\Leftrightarrow\frac{x-1}{\left(x+1\right)\left(x^2+x+2\right)}>0\Rightarrow\left[{}\begin{matrix}x>1\\x< -1\end{matrix}\right.\)
\(A=\frac{2sinx.cosx+sinx}{1+2cos^2x-1+cosx}=\frac{sinx\left(2cosx+1\right)}{cosx\left(2cosx+1\right)}=\frac{sinx}{cosx}=tanx\)
\(B=\frac{cosa}{sina}\left(\frac{1+sin^2a}{cosa}-cosa\right)=\frac{cosa}{sina}\left(\frac{1+sin^2a-cos^2a}{cosa}\right)=\frac{cosa}{sina}.\frac{2sin^2a}{cosa}=2sina\)
\(C=\frac{1+cos2x+cosx+cos3x}{2cos^2x-1+cosx}=\frac{1+2cos^2x-1+2cos2x.cosx}{cos2x+cosx}=\frac{2cosx\left(cosx+cos2x\right)}{cos2x+cosx}=2cosx\)
\(D=\frac{2sinx.cosx.\left(-tanx\right)}{-tanx.sinx}-2cosx=2cosx-2cosx=0\)
\(E=cos^2x.cot^2x-cot^2x+cos^2x+2cos^2x+2sin^2x\)
\(E=cot^2x\left(cos^2x-1\right)+cos^2x+2=\frac{cos^2x}{sin^2x}\left(-sin^2x\right)+cos^2x+2=2\)
\(F=\frac{sin^2x\left(1+tan^2x\right)}{cos^2x\left(1+tan^2x\right)}=\frac{sin^2x}{cos^2x}=tan^2x\)
Câu G mẫu số có gì đó sai sai, sao lại là \(2sina-sina?\)
\(H=sin^4\left(\frac{\pi}{2}+a\right)-cos^4\left(\frac{3\pi}{2}-a\right)+1=cos^4a-sin^4a+1\)
\(=\left(cos^2a-sin^2a\right)\left(cos^2a+sin^2a\right)+1=cos^2a-\left(1-cos^2a\right)+1=2cos^2a\)