x²+3分之x-2y的值为0
∵x²+3>0
∴x-2y=0
∴x=2y
x²-y²分之x²-3xy-4y²
=(x-4y)(x+y)/(x+y)(x-y)
=(x-4y)/(x-y) x=2y
=(2y-4y)/(2y-y)
=-2