Bài 2:
\(a,=x\left(x+7\right)\\ b,=x\left(x^2+4x+4\right)=x\left(x+2\right)^2\)
Bài 3:
\(a,\Leftrightarrow\left(x-3\right)\left(x+5\right)=0\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-5\end{matrix}\right.\\ b,\Leftrightarrow x^2-x-2x+2=0\\ \Leftrightarrow\left(x-2\right)\left(x-1\right)=0\Leftrightarrow\left[{}\begin{matrix}x=1\\x=2\end{matrix}\right.\)
Bài 4:
\(a,\widehat{D}=360^0-\widehat{A}-\widehat{B}-\widehat{C}=150^0\)
\(b,\dfrac{x+10}{2}=12\Leftrightarrow x+10=24\Leftrightarrow x=14\left(cm\right)\)
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