若X+7Y=Y-3X,求X的平方减Y的平方除以X的平方加Y的平方的差

因为X+7Y=Y-3X,
所以4X=-6Y,
所以X=-3Y/2,
所以(X^2-Y^2)/(X^2+Y^2)
=[(-3Y/2)^2-Y^2]/[(-3Y/2)^2+Y^2]
=(9Y^2/4-Y^2)/(9Y^2/4+Y^2)
=(5Y^2/4)/(13Y^2/4)
=(5Y^2/4)*(4/13Y^2)
=5/13.

X+7Y=Y-3X
4x=6y
x=3y/2
你写的不清楚，
是(X^2-Y^2)/(X^2+Y^2)
=(9Y^2/4-Y^2)/(9Y^2/4+Y^2)
=5/13
还是X^2-Y^2/(X^2+Y^2)
=9Y^2/4-Y^2/(9Y^2/4+Y^2)
=9Y^2/4-4/13

X+7Y=Y-3X =>6Y=-4X =>Y=-2/3X

(X^2-Y^2)/(X^2+Y^2)
=(X^2-4/9X^2)/(X^2+4/9X^2)
=5/13

解： 4x=8y x=2y

那么 (x^2-y^2)/(x^2+y^2)
=3y^2/5y^2=3/5

问你老师.

负1