`B1.`
`1)`
`x.(a-b) + a-b`
`=(a-b)(x+1)`
`2)`
`m.(x+y)+x+y`
`=(x+y)(m+1)`
`3)`
`x.(a+b)-a-b`
`=x.(a+b)-(a+b)`
`=(a+b)(x-1)`
`4)`
`ax+ay-2x-2y`
`=a(x+y) -2(x+y)`
`=(x+y)(a-2)`
`5)`
`a²-4b²`
`=a²-(2b)²`
`=(a-2b)(a+2b)`
`6)`
`(a+b)²-4`
`=(a+b)²-2²`
`=(a+b+2)(a+b-2)`
`B2.`
`1)`
`x² -7x=0`
`⇔x(x-7)=0`
`⇔` $\left[\begin{matrix} x=0\\ x-7=0\end{matrix}\right.$
`⇔` $\left[\begin{matrix} x=0\\ x=7\end{matrix}\right.$
`⇒S={0;7}`
`2)`
`x² +3x-2x-6=0`
`⇔x(x +3) - 2(x+3)=0`
`⇔(x+3)(x-2)=0`
`⇔`$\left[\begin{matrix} x+3=0\\ x-2=0\end{matrix}\right.$
`⇔` $\left[\begin{matrix} x=-3\\ x=2\end{matrix}\right.$
`⇒S={-3;2}`
`3)`
`x² -81=0`
`⇔x²-9²=0`
`⇔(x-9)(x+9)=0`
`⇔`$\left[\begin{matrix} x-9=0\\ x+9=0\end{matrix}\right.$
`⇔` $\left[\begin{matrix} x=9\\ x=-9\end{matrix}\right.$
`⇒S={-9;9}`
