求正确答案,还要有式子!
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求正确答案,还要有式子!求正确答案,还要有式子! 求正确答案,还要有式子!x^2+xy+y^2=x^2+2xy+y^2-xy=(x+y)^2-xyx=√2+1y=√2-1x+y=2√2xy=
求正确答案,还要有式子!
求正确答案,还要有式子!
求正确答案,还要有式子!
x^2+xy+y^2
=x^2+2xy+y^2-xy
=(x+y)^2-xy x=√2+1 y=√2-1 x+y=2√2 xy=1
=(2√2)^2-1
=8-7
=7
3(a+1)^2-(a+1)(2a-1)
=3(a^2+2a+1)-(2a^2+a-1)
=3a^2+6a+3-2a^2-a+1
=a^2+5a+4
=(a+1)(a+4) a=1
=2*5
=10
x-y=2，xy=1
x²+xy+y²=（x-y）²+3xy=4+3=7