求定积分∫上5下-2|x平方-2x-3|dx

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求定积分∫上5下-2|x平方-2x-3|dx
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求定积分∫上5下-2|x平方-2x-3|dx
求定积分∫上5下-2|x平方-2x-3|dx

求定积分∫上5下-2|x平方-2x-3|dx

见图

x^2-2x-3=(x-1)^2-4
∫(x-1)^2-4dx=(x-1)^3/3-4(x-1)+C
∫4-(x-1)^2dx=4(x-1)-(x-1)^3/3+C
x<-1,x^2-2x-3<0,-10,x>3,x^2-2x-3<0
∫[-2,5] |x^2-2x-3|dx
=∫[-2,-1] [4-(x...

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x^2-2x-3=(x-1)^2-4
∫(x-1)^2-4dx=(x-1)^3/3-4(x-1)+C
∫4-(x-1)^2dx=4(x-1)-(x-1)^3/3+C
x<-1,x^2-2x-3<0,-10,x>3,x^2-2x-3<0
∫[-2,5] |x^2-2x-3|dx
=∫[-2,-1] [4-(x-1)^2]d(x-1) +∫[-1,3] [(x-1)^2-4] d(x-1)+∫[3,5] 4-(x-1)^2d(x-1)
=4*[(-1-1)-(-2-1)]+[-(-1-1)^3/3+(-2-1)^3/3] +[(3-1)^3/3-(1+1)^3/3]+4[2-(3-1)]+ 4[(5-1)-(3-1)]+[-(5-1)^3/3+(3-1)^3/3]
=4+(8/3-27/3)+4*2+(-64/3+8/3)
=12+(-19-56)/3=12-25=-13

收起

利用定积分的区间可加性去绝对值。解答如下:
∫上5下-2|x平方-2x-3|dx
=∫上-1下-2|x平方-2x-3|dx+∫上3下-1|x平方-2x-3|dx+∫上5下3|x平方-2x-3|dx
=[x^3/3-x^2-3x]上-1下-2+[x^3/3-x^2-3x]上3下-1+[x^3/3-x^2-3x]上5下3
=1-32/3+32/3
=1