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若x+y=3,则x²-y²+6y=
人气:166 ℃ 时间:2020-02-02 15:03:02
解答
答:
x+y=3
x²-y²+6y
=(x-y)(x+y)+6y
=3(x-y)+6y
=3x-3y+6y
=3x+3y
=3(x+y)
=3*3
=9
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