To solve this you have to apply the quotient rule: $D _{x}\left[ \frac{ f(x) }{ g(x) } \right]=\frac{ f ^{\prime}(x)g(x)-f(x)g ^{\prime}(x) }{ \left[ g(x) \right]^{2} }$ $D _{x}\left[ \frac{ (1-x) }{ (1+x) } \right]=\frac{ -1(1+x)-(1-x)1 }{ [1]^2 }$This simplifies to...$D _{x}=-2$Now we can insert our derivative and point into the point-slope form:$y-y _{1}=m \left( x-x _{1} \right)$ $-3 - y _{1}=-2\left( -2-x _{1} \right)$...which simplifies to your solution:$y=-2x-7$I hope this helped!