搜狗做题网请教一道数学题(关于函数)
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请教一道数学题(关于函数)
设D(x,y)
DE=OF=x DF=OE=y
OE^2+OF^2=EF^2=9
x^2+y^2=9
y=-x+b x+y=b
B(-2,-2)
A(-2,y) C(x,-2)
AC经过坐标原点
y/(-2)=(-2)/x
xy=4
x^2+y^2=9
(x+y)^2=x^2+2xy+y^2=9+8=17
(x-y)^2=x^2-2xy+y^2=9-8=1
x+y=根号17
x-y=1
x+y=b=根号17
|S△NED-S△DFM|=|(b-y)x/2-(b-x)y/2|=|(bx-xy-by+xy)/2|=|(x-y)b/2|=b/2=根号17/2
选B
DE=OF=x DF=OE=y
OE^2+OF^2=EF^2=9
x^2+y^2=9
y=-x+b x+y=b
B(-2,-2)
A(-2,y) C(x,-2)
AC经过坐标原点
y/(-2)=(-2)/x
xy=4
x^2+y^2=9
(x+y)^2=x^2+2xy+y^2=9+8=17
(x-y)^2=x^2-2xy+y^2=9-8=1
x+y=根号17
x-y=1
x+y=b=根号17
|S△NED-S△DFM|=|(b-y)x/2-(b-x)y/2|=|(bx-xy-by+xy)/2|=|(x-y)b/2|=b/2=根号17/2
选B