已知a+b=7,ab=10,则(a-b)²=_______.

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已知a+b=7,ab=10,则(a-b)²=_______.
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已知a+b=7,ab=10,则(a-b)²=_______.
已知a+b=7,ab=10,则(a-b)²=_______.

已知a+b=7,ab=10,则(a-b)²=_______.

(a-b)²
=(a+b)²-4ab
=7²-4×10
=49-40
=9

解由
(a-b)²
=a²-2ab+b²
=a²+2ab+b²-4ab
=(a+b)²-4ab
=7²-4×10
=9

答:
a+b=7,ab=10
(a-b)²
=a²-2ab+b²
=a²+2ab+b²-4ab
=(a+b)²-4ab
=7²-4*10
=49-40
=9
已知a+b=7,ab=10,则(a-b)²=____9___

(a-b)^2=a^2-2ab+b^2=(a+b)^2-4ab=7^2-4*10=9