\(a,\left(x+1\right)\left(2-x\right)-\left(3x+5\right)\left(x+2\right)=-4x^2+2\)
\(\Rightarrow2x-x^2+2-x-3x^2-6x-5x-10+4x^2-2=0\)
\(\Rightarrow-10x-10=0\)
\(\Rightarrow-10\left(x+1\right)=0\)
\(\Rightarrow x+1=0\)
\(\Rightarrow x=-1\)
\(b,x^2-5x-3=0\) câu này đề sai
Mk làm câu tương tự , bn xem lại đề r tự lm nhé
\(x^2-4x+3=0\)
\(\Rightarrow x^2-3x-x+3=0\)
\(\Rightarrow\left(x^2-3x\right)-\left(x-3\right)=0\)
\(\Rightarrow x\left(x-3\right)-\left(x-3\right)=0\)
\(\Rightarrow\left(x-3\right)\left(x-1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x-3=0\\x-1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=3\\x=1\end{matrix}\right.\)
