已知x+y=1/2,xy=3/8,求下列各式的值(1)(x-y)^2 (2)x^2y+xy^2

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已知x+y=1/2,xy=3/8,求下列各式的值(1)(x-y)^2 (2)x^2y+xy^2

(1) (x-y)²
=x²-2xy+y²
=x²+2xy+y²-4xy
=(x+y)²-4xy
=(1/2)²-4×3/8
=1/4-3/2
=-5/4
(2)x^2y+xy^2
=xy(x+y)
=3/8×1/2
=3/16

你用假设法 X=1/8 y=3/8,或者相反。然后带进去算吧