先求里面的积分
∫(0,x)(x^2+xy/2)dy
=(x^2y +xy^2/4) (0,x)
=x^3+x^3/4
=5x^3/4
所以原式=6/7*5/4*∫(0,1)x^3dx
=15/14*x^4/4(0,1)
=15/56