x ( a + 1 ) + 4 = a ( a − 3 + x ) x a + x = a 2 − 3 a + a x − 4 x = a 2 3 a − 4 ↓ | a 2 − 3 a − 4 | < 6 − 6 < a 2 − 3 a − 4 < 6 {\displaystyle {\begin{aligned}&x(a+1)+4=a(a-3+x)\\&xa+x=a^{2}-3a+ax-4\\&x=a^{2}3a-4\\&\downarrow \\&|a^{2}-3a-4|<6\\&-6<a^{2}-3a-4<6\\\end{aligned}}}
a 2 − 3 a − 4 < 6 a 2 − 3 a − 10 < 0 ( a + 2 ) ( a − 5 ) < 0 ( a + 2 ) ( a − 5 ) = 0 x 1 = − 2 x 2 = 5 ↓ − 2 < a < 5 {\displaystyle {\begin{aligned}&a^{2}-3a-4<6\\&a^{2}-3a-10<0\\&(a+2)(a-5)<0\\&(a+2)(a-5)=0\\&x_{1}=-2&x_{2}=5\\&\downarrow \\&-2<a<5\end{aligned}}}
− 2 < a < 1 ; 2 < a < 5 {\displaystyle {\begin{aligned}-2<a<1;2<a<5\end{aligned}}}
