a²+ab=20 ab-b²=13 求a²+b² a²+b² 和a²+2ab-b²的值
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a²+ab=20 ab-b²=13 求a²+b² a²+b² 和a²+2ab-b²的值
a²+ab=20 ab-b²=13 求a²+b² a²+b² 和a²+2ab-b²的值
a²+ab=20 ab-b²=13 求a²+b² a²+b² 和a²+2ab-b²的值
a²+ab=20 .式1
ab-b²=13 .式2
式1+式2=a²+2ab-b²=33(第二问答案)
a²+b²=(a²+ab)-(ab-b²)=20-13=7
a²+2ab-b²=(a²+ab)+(ab-b²)=20+13=33
a²+ab=20 ①
ab-b²=13 ②
a²+b²
=(a²+ab)-(ab-b²)
=20-13
=7
a²+2ab-b²
=(a²+ab)+(ab-b²)
=20+13
=33
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a²+ab=20 ①
ab-b²=13 ②
a²+b²
=(a²+ab)-(ab-b²)
=20-13
=7
a²+2ab-b²
=(a²+ab)+(ab-b²)
=20+13
=33
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a²+b²
=a²+ab-ab+b²
=(a²+ab)-(ab-b²)
=20-13
=7
a²+2ab-b²
=a²+ab+ab-b²
=(a²+ab)+(ab-b²)
=20+13
=33
a²+ab=20…………①
ab-b²=13 …………②
①-②得
a²+b²=7
①+②得
a²+2ab-b²=33