若a+b=7,ab=5,求(a-b)^2的值
问题描述：
若a+b=7,ab=5,求(a-b)^2的值
答
=a^2-2ab+b^2+4ab-4ab
=(a+b)^2-4ab
=7^2-4*5
=49-20
=29
答
（a-b^2=(a+b)^2-4ab=49-20=29
答
(a-b)2=a2-2ab+b2=a2+2ab+b2-4ab=(a+b)2-4ab=49-4*5=29
答
(a-b)^2=a²-2ab+b²=a²+2ab+b²-4ab=(a+b)²-4ab=7²-4×5=29
答
因a+b=7
（a+b）^2=49
a^2+2ab+b^2=49
a^2+b^2=49-2ab
(a-b)^2
=a^2+b^2-2ab
=49-2ab-2ab
=49-4ab=49-4x5=49-20=29
答
(a-b)^2=(a+b)²－4ab
=7²－4×5
=49－20
=29