^是几次方的意思,如5^3=125

　　圆环面积=πx^2-πy^2=π(x+y)(x-y)=14π

　　所以(x+y)(x-y)=14

　　原式=[-6(x+y)^2*(x-y)^3]^2/[3(x+y)(x-y)^2]^2

　　=36(x+y)^4*(x-y)^6/[9(x+y)^2*(x-y)^4]

　　=4(x+y)^2*(x-y)^2

　　=4[(x+y)(x-y)]^2

　　=196*4

　　=784