(а-1/a^2)*(ax-a/a-1)+(x-1/2a)=((a-1)*a(x-1)/a^2*(a-1))+((1-x)/2a)=((x-1)/a)+((1-x)/2a)=
=((2x-2)/2a)+((1-x)/2a)=((2x-2+1-x)/2a)=x-1/2a
"/"-дробь
4х²-36х+81=4х²-12х+9
4х²-4х²-36х+12х+81-9=0
-24х=72
х=-3
-3х^2+7х+45=(х+6)^2
-3х^2+7х+45=х^2+12х+36
х^2+12х+36+3х^2-7х-45=0
4х^2+5х-9=0
д=25-4×4×(-9)=169
х1=(-5-13)/2×4=-18/8=-2 1/4
х2=(-5+13)/2×4=1