(x-y)^2
=x^2-2xy+y^2
=x^2+2xy+y^2-4xy
=(x+y)^2-4xy
=a^2-4b
x^2+y^2
=x^2+y^2+2xy-2xy
=(x+y)^2-2xy
=a^2-2b
x^2-xy+y^2
=x^2+2xy+y^2-3xy
=(x+y)^2-3xy
=a^2-3b
已知x+y=a,xy=b,求(x-y)^2,x^2+y^2,x^2-xy+y^2的值
已知x+y=a,xy=b,求(x-y)^2,x^2+y^2,x^2-xy+y^2的值
数学人气:568 ℃时间:2020-02-05 22:34:36
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