它们交于(1,-2)、(4,4),
因此 S=∫[-2,4] [(y+4)/2-y^2/4]dy = y^2/4+2y-y^3/12 | [-2,4] = 9 .
如果以 x 为积分变量,则 S=∫[0,1] 2√(4x) dx+∫[1,4] [√(4x)-(2x-4)]dx
= 8/3*x^(3/2) | [0,1] +4/3*x^(3/2)-x^2+4x | [1,4]
=(8/3-0)+(32/3-16+16)-(4/3-1+4)
=9 .
它们交于(1,-2)、(4,4),
因此 S=∫[-2,4] [(y+4)/2-y^2/4]dy = y^2/4+2y-y^3/12 | [-2,4] = 9 .
如果以 x 为积分变量,则 S=∫[0,1] 2√(4x) dx+∫[1,4] [√(4x)-(2x-4)]dx
= 8/3*x^(3/2) | [0,1] +4/3*x^(3/2)-x^2+4x | [1,4]
=(8/3-0)+(32/3-16+16)-(4/3-1+4)
=9 .