举报
泛舟于涯
你手机不支持么次方格式么?? ∫∫ x^2e^(- y^2) dxdy = ∫(0→1) e^(- y^2) dy ∫(0→y) x^2 dx = ∫(0→1) e^(- y^2) * 1/3 * y^3 dy = (1/3)∫(0→1) e^(- y^2) * y^2 * (- 1/2) d(- y^2) = (- 1/6)∫(0→1) y^2 d[e^(- y^2)] = (- 1/6)y^2e^(- y^2):(0→1) + (1/6)∫(0→1) e^(- y^2) d(y^2) = (- 1/6)e^(- 1) - (1/6)∫(0→1) e^(- y^2) d(- y^2) = - 1/(6e) - (1/6)e^(- y^2):(0→1) = - 1/(6e) - (1/6)[e^(- 1) - 1] = - 1/(6e) - 1/(6e) + 1/6 = 1/6 - 1/(3e)