(3-4cos2a+2cos²2a-1)/(3+4cos2a+2cos²2a-1)=
=(2cos²2a-4cos2a+2)/2cos²2a+4cos2a+2)=
=2(cos²2a-2cos2a+1)/2(cos²2a+2cos2a+1)=(cos2a-1)²/(cos2²+1)²=
=(-2sin²a)²/(2cos²a)²=4sin^4a/4cos^4a=tg^4a
=m*(n^2-m^2-12m-36) Вроде так
0,4х²+3х=0
х(0,4х+3)=0
х1=0
0,4х+3=0
0,4х=-3
х2=-3/0,4=7,5