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Homework Statement
find dy/dx
yx2+ xy2=7
Homework Equations
The Attempt at a Solution
xy(x+y)=7
2xy=(x+y) (x+y) = 7
2xy + x2+2xy +y2=0
2xy + dx/dy(x2+2xy+y2)=0
2xy +x2+dy/dx 2xy + dy/dx y2
dy/dx = (-2xy-x2)/(2xy + y2)
The answer is actually (-y2+2xy)/(x2+2xy)
Can anybody tell me what I'm doing wrong/how to swap the answer?