化为累次积分,先对y再对x
∫dx∫(x^2+y^2)dy=∫dx[x^2y+y^3/3](从0到x^2)
=∫dx[x^2y+y^3/3](从0到x^2)=∫dx*(x^4+x^6/3)
=[x^5/5+x^7/21](从0到1)=1/5+1/21=26/105