a, $x²-5x=0$
⇔ $x.(x-5)=0$
⇔ \(\left[ \begin{array}{l}x=0\\x-5=0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=0\\x=5\end{array} \right.\)
b, $|7x-2|=19$
⇔ \(\left[ \begin{array}{l}7x-2=19\\7x-2=-19\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=3\\x=-17/7\end{array} \right.\)
c, $x+7=y.(x-2)$
⇔ $x+7=xy-2y$
⇔ $x-xy+2y=-7$
⇔ $x.(1-y)-2+2y=-9$
⇔ $(x-2).(1-y)=-9$
⇔ $(x-2).(y-1)=9=1.9=9.1=(-1).(-9)=(-9).(-1)=3.3=(-3).(-3)$
d, $x+9=y.(x-4)$
⇔ $x-xy+4y=-9$
⇔ $x.(1-y)-4+4y=-9$
⇔ $(x-4).(y-1)=9=1.9=9.1=(-1).(-9)=(-9).(-1)=3.3=(-3).(-3)$
e, $xy=x+y$
⇔ $x-xy+y=0$
⇔ $x.(1-y)-1+y=-1$
⇔ $(x-1).(y-1)=1=1.1=(-1).(-1)$
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