Question

решите уравнение(х^2-9x)(x^2-9x-12)=160

Answer 1

x²-9x=t

t(t-12)=160
t²-12t-160=0
D=12²+4*160=28²
t_1=(12+28)/2=20                  t_2=(12-28)/2=-8
  x²-9x=20                                  x²-9x=-8
   x²-9x-20=0                                x²-9x+8=0
     D=81+80=161                           D=81-32=49
x_1=(9+√161)/2                               x_3=(9+7)/2=8
  x_2=(9-√161)/2                               x_4=(9-7)/2=1