1) 12-x^2=11, отсюда x1=1, x2=-1.
2) 18-x^2=14 x1=2 x2=-2
3) 225-100*x^2=0, тут 100*x^2=225, x^2=2.25, x1=-1.5 x2=1.5
4) 4-36*x^2=0 x1=-1/3 x2=1/3
5) x^2+2=x+2 x1=-1 x2=1
6) 2*x^2-14=0 x1=-(7)^0.5 x2=7^0.5
7) 3*x^2-6=0 x1=-(2)^0.5 x2=2^0.5
8) 4*x^2-12=0 x1=-(3)^0.5 x2=3^0.5