下图的结果是怎么算出的 请写出(详细过程)谢谢 紧急求助 (高等数学 ,理工学科)!
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(u/v)' = (u'v - uv')/v^2
∂P/∂y = {d(x+ay)/dy (x+y)^2 - (x+ay) d((x+y)^2)/dy } /(x+y)^4
= {a(x+y)^2 - (x+ay) 2(x+y) }/(x+y)^4
= (ax + ay - 2x - 2ay)/(x+y)^3
= (a(x-y) - 2x)/(x+y)^3
∂Q/∂y = {dy/dy (x+y)^2 - y d((x+y)^2)/dy } /(x+y)^4
= {(x+y)^2 - y 2(x+y) }/(x+y)^4
= (x+y - 2y)/(x+y)^3
= (x-y)/(x+y)^3
∂P/∂y = {d(x+ay)/dy (x+y)^2 - (x+ay) d((x+y)^2)/dy } /(x+y)^4
= {a(x+y)^2 - (x+ay) 2(x+y) }/(x+y)^4
= (ax + ay - 2x - 2ay)/(x+y)^3
= (a(x-y) - 2x)/(x+y)^3
∂Q/∂y = {dy/dy (x+y)^2 - y d((x+y)^2)/dy } /(x+y)^4
= {(x+y)^2 - y 2(x+y) }/(x+y)^4
= (x+y - 2y)/(x+y)^3
= (x-y)/(x+y)^3
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