y=√(x^2-4)+√(4-x^2)+(x^2+x+8)/(2+x)
∵x^2-4≥0,4-x^2≥0,x+2≠0
∴x^2-4=0,x≠-2
x=2
y=0+0+(2^2+2+8)/(2+2)=7/2
x√y+y√x-√56=2√(7/2)+7/2√2-2√14=7/2√2-√14