已知:x=3,y=-5,x2-2xy+y2/x2-y2的值是已知:x=3,y=-5,x²-2xy+y²/x²-y²的值是

问题描述:

已知:x=3,y=-5,x2-2xy+y2/x2-y2的值是
已知:x=3,y=-5,x²-2xy+y²/x²-y²的值是

已知:x=3,y=-5,x²-2xy+y²/x²-y²的值是

原式=3²-2*3*(-5)+(-5²)/3²-(-5²)
=9+30+(-25)/34
=39+(-25/34)
=39-25/34
=38又9/34

x²-2xy+y²/x²-y²
=(x-y)²/(x-y)(x+y)
=(x-y)/(x+y)
因为x=3,y=-5,
所以(3-(-5))/(3+(-5))
=8/(-2)
=-4