(a*b)*c=0
(a*b)*c==-40+2+4a+4a+5=0
+8a-33=0
=64-4*1*(-33)=64+132=169
D=14
a1=-8+14/2=6/2=3
a2=-8-14/2=-22/2=-11
(a*b)*c=0
(a*b)*c=![\left[\begin{array}{ccc}1&2&4\\-2&a&-1\\-1&5&a\end{array}\right]](/tpl/images/0947/5494/3ef32.png)
=
-40+2+4a+4a+5=0
D=14
a1=-8+14/2=6/2=3
a2=-8-14/2=-22/2=-11