宜用Y型区域：∫∫ (x² + y² - y) dσ= ∫(0→2) dy∫(y→2y) (x² + y² - y) dx= ∫(0→2) [x³/3 + xy² - xy] |(y→2y) dy= (1/3)∫(0→2) (10y³ - 3y²) dy= (1/3)[10y⁴/4 - y³] |(0→2)= (1/3)(32)= 32/3
