\(6,=\left(x-2y\right)\left(5x^2-15x\right)=5x\left(x-3\right)\left(x-2y\right)\left(C\right)\\ 7,\Leftrightarrow x\left(x-5\right)=0\Leftrightarrow\left[{}\begin{matrix}x=0\\x=5\end{matrix}\right.\left(D\right)\\ 8,=x^2-20x+100+1=\left(x-10\right)^2+1>0\left(A\right)\\ 9,\widehat{D}=360^0-120^0-80^0-100^0=60^0\left(D\right)\\ 10,D\)
câu 6;
\(5x^2\left(x-2y\right)-15x\left(x-3y\right)=\left(5x^2-15x\right)\left(x-2y\right)=5x\left(x-3\right)\left(x-2y\right)\)
câu 7:
\(x^2-5x=0\\ \Leftrightarrow x\left(x-5\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=5\end{matrix}\right.\)
Câu 8:
\(x^2-20x+101=\left(x^2-20x+100\right)+1=\left(x-10\right)^2+1>0\)
\(\Rightarrow x^2-20x+101\) luôn dương
Câu 9:
\(\widehat{D}=360^o-120^o-80^o-100^o=60^o\)
Câu 10:D
