[(x+2y)²-(x+y)(3x-y)-5y²]÷(2x),其中x,y满足x²+4x+y
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[(x+2y)²-(x+y)(3x-y)-5y²]÷(2x),其中x,y满足x²+4x+y²-y+17/4=0

将x²+4x+y²-y+17/4=0配方成(x+2)^2+(y-1/2)^2=0

可得x=-2,y=-1/2

[(x+2y)²-(x+y)(3x-y)-5y²]÷(2x)

=[x^2+4xy+4y^2-3x^2-2xy+y^2-5y^2]/(2x)

=(-2x^2+2xy)/(2x)

=-x+y

=2-1/2

=3/2

已知、x+y=6且xy=4

(1)x²+y² (2)(x-y)² (3)x{四次方}+y{四次方}

(1)x²+y²=(x+y)²-2xy=36-8=28

(2)(x-y)²=(x+y)²-4xy=36-16=20

(3)x^4+y^4=(x^2+y^2)^2-2x²y²=28*28-2*16=784-32=752