(X/4)^2+[(56-X)/4]^2=200
x^2/16+(56-x)^2/16=200
x^2+(56-x)^2=3200
x^2+3136-112x+x^2=3200
2x^2-112x-64=0
x^2-56x-32=0
判别式=56^2+4*32=3264
x=(56±8√51)/2=28±4√51
x=-0.5657,x=56.5657