( 5х - 1 )( Х + 2 ) + 3( Х - 4 )( Х + 4 ) = 2( 2х + 3 )^2 - 8
5х^2 + 10х - Х - 2 + 3( х^2 - 16 ) = 2( 4х^2 + 12х + 9 ) - 8
5х^2 + 9х - 2 + 3х^2 - 48 = 8х^2 + 24х + 18 - 8
8х^2 + 9х - 50 = 8х^2 + 24х + 10
9х - 50 = 24х + 10
24х - 9х = - 50 - 10
15х = - 60
Х = - 60 : 15
Х = - 4