(x-10)^2+(x+9)^2=2x^2
x^2-20x+100+x^2+18x+81-2x^2=0
-2x+181=0
x=181/2=90,5
(x-5)^2+(x+4)^2=2x^2
x^2-10x+25+x^2+8x+16-2x^2=0
-2x+41=0
x=41/2=20,5
x^2-3x-40=0
D=9+160=169
x1=(3+13)/2=8
x2=(3-13)/2=-5
x^2+7x+6=0
D=49-24=25
x1=(-7+5)/2=-1
x2=(-7-5)/2=-6
x^2+6x+9=0
D=36-36=0
x=-6/2=-3
x^2+3x-54=0
D=9+4*54=225
x1=(-3+15)/2=6
x2=(-3-15)/2=-9