+118680 Here is a question that I am stumped on.
I put the equation into Desmos and it really is two straight lines. 
The angle between them appears to be always 90 degrees.
https://www.desmos.com/calculator/dvnoukkszg
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What is the equation of the two straight lines represented by the equation
\(ab (x^2-y^2) + (a^2-b^2)xy=0\)
Also, find the angle between them?
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From the graph I can see that the lines are y=mx and y=-x/m
But how do I rearrange to get this?
