Объяснение:
11. -x*(x+99)+(x-10)(x-10)=-x²-99x+x²-100=-99x-100=-99*(-8/9)-100=
=11*8-100=88-100=-12.
11. (a-10)²-20*(6-a)=a²-20a+100-120+20a=a²-20=(30/7)²-20=
=(900/49)-20=(900-20*49)/49=(900-980)/49=-80/49.
