a+b=6,ab=27,求a^2+b^2-ab？
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a^2+b^2-ab=a^2+2ab+b^2-3ab=(a+b)^2-3ab=36-81=-45,10,a^2+b^2-ab
=a^2+b^2+2ab-3ab
=(a+b)^2-3ab
=6^2-3×7
=36-21
=15,2,a^2+b^2-ab
=a^2+b^2+2ab-3ab
=(a+b)^2-3ab
=6^2-3x27
=36-81
=-45,1,（a+b）*（a+b）=a^2+b^2+2ab =36
a^2+b^2=36-2ab=-8
a^2+b^2-ab =-8-27=-35
则题有误,0,
=a^2+b^2+2ab-3ab
=(a+b)^2-3ab
=6^2-3×7
=36-21
=15,2,a^2+b^2-ab
=a^2+b^2+2ab-3ab
=(a+b)^2-3ab
=6^2-3x27
=36-81
=-45,1,（a+b）*（a+b）=a^2+b^2+2ab =36
a^2+b^2=36-2ab=-8
a^2+b^2-ab =-8-27=-35
则题有误,0,
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