(х+5)(х+3)(х-2)(х-4)=-48
(х+5)(х-4)=х^2+x-20=t
(х+3)(х-2)=х^2+x-6=t+14
(х+5)(х+3)(х-2)(х-4)=t*(t+14)=-48
t*(t+14)=-48
t=-6 или t=-8
х^2+x-20=-6 или х^2+x-20=-8
х^2+x-14=0 или х^2+x-12=0
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x1=(-1-корень(57))/2
x2=(-1+корень(57))/2
x3=-4
x4=3