x2 + 17x +72 =0
=> x2+9x+8x+72
=> x(x+9)+8(x+9)=0
=> (x+8)(x+9)=0
=> \(\left[{}\begin{matrix}x+8=0\\x+9=0\end{matrix}\right.\) => \(\left[{}\begin{matrix}x=-8\\x=-9\end{matrix}\right.\)
vậy x=-8 hoặc x=-9
2x2 -7x +3 =0
=> 2x2-x-6x+3=0
=> x(2x-1)-3(2x-1)=0
=> (x-3)(2x-1)=0
=> \(\left[{}\begin{matrix}x-3=0\\2x-1=0\end{matrix}\right.\) => \(\left[{}\begin{matrix}x=3\\2x=1\Rightarrow x=\dfrac{1}{2}\end{matrix}\right.\)
vậy x=3 hoặc x=\(\dfrac{1}{2}\)
