计算∫(2x-y)dx (x 3y)dy,L为正向圆周x² y²=4
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取x=sint+1(-pi/2
P=x^2+3y,Q=y^2-xPy=3Qx=-1∫L(x^2+3y)dx+(y^2-x)dy+∫AO(x^2+3y)dx+(y^2-x)dy=-4∫∫Ddxdy=-16π∫AO(x^2+3y)dx+
原式=∫dy∫e^(-y²/2)dx(作积分顺序变换)=∫(1-y²)e^(-y²/2)dy=∫e^(-y²/2)dy-∫y²e^(-y²/
题目应该是e^(-y^2)交换积分次序:=∫(0,1)dy∫(0,y)e^(-y^2)dx=∫(0,1)ye^(-y^2)dy=1/2*∫(0,1)e^(-y^2)dy^2=1/2*(1-1/e)
[x(x2y2-xy)-y(x2+x3y)]÷3x2y,=(x3y2-x2y-x2y-x3y2)÷3x2y,=-2x2y÷3x2y,=-23.
积分区域D:x-1≤y≤2,1≤x≤3视为Y型区域,即:1≤x≤y+1,0≤y≤2I=∫[0,2]sin(y²)dy∫[1,y+1]dx交换积分次序=∫[0,2]ysin(y²)d
∫(2-xsinx)/xdx=∫(2/x-sinx)dx=2lnx+cosx+C
把积分区域D画图,改换积分次序:∫(0~1)dx∫(x~1)e^(-y^2)dy=∫(0~1)dy∫(0~y)e^(-y^2)dx=∫(0~1)ye^(-y^2)dy被积函数的原函数是-1/2e^(-
∫(x=1→3)dx∫(y=x-1→2)e^(y²)dy交换积分次序:dydx→dxdyx=1到x=3,y=x-1到y=2y=0到y=2,x=1到x=y+1=∫(y=0→2)e^(y
原式=4x29y2•27y364x3•4xy=34x2.故答案为34x2.
(2x4-4x3y-x2y2)-2(x4-2x3y-y3)+x2y2=2x4-4x3y-x2y2-2x4+4x3y+2y3+x2y2=2y3,因为化简的结果中不含x,所以原式的值与x值无关.
原式=(x3y2-x2y-x2y+x3y2)÷3x2y=(2x3y2-2x2y)÷3x2y=23xy-23.
已知x+y=5,xy=3,代数式x3y-2x平方y平方+xy3=xy(x²-2xy+y²)=xy(x-y)²=3×[(x+y)²-4xy]=3×(25-12)=
x+y=4,xy=2后者平方后二式相加再加后者平方
x3y+xy3=xy(x^2+y^2)=(√3-√2)(√3+√2)((√3-√2)^2)+(√3-√2)^2)=1*(3-2√6+2+3+2√6+2)=10
(1)原式=x2-(2y-3)2=x2-4y2+12y-9;(2)原式=4x6y2•(-2xy)-8x9y3÷(2x2)=-8x7y3-4x7y3=-12x7y3.
∵x-y=l,xy=2,∴x3y-2x2y2+xy3=xy(x2-2xy+y2)=xy(x-y)2=2×1=2.