若a+b=5,ab=6,求a²+3ab+b²的值(过程)
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若a+b=5,ab=6,求a²+3ab+b²的值(过程)
若a+b=5,ab=6,求a²+3ab+b²的值(过程)
若a+b=5,ab=6,求a²+3ab+b²的值(过程)
a+b=5
(a+b)^2=5^2=25
a^2+2ab+b^2=25 (1)
把ab=6代入(1)
a^2+b^2=25-2*6=13 (2)
把(2)式和ab=3代入:
a^2+3ab+b^2=13+3*6=13+18=31
所以a^2+3ab+b^2的值是31
a²+3ab+b²
=a²+2ab+b²+ab
=(a+b)²+ab
=5²+6
=31
a^2+2ab+b^2+ab
=(a+b)^2+ab
=25+6
=31
a²+3ab+b²
=a^2+2ab+b^2+ab
=(a+b)^2+ab
=25+6
=31
a²+3ab+b²
=a²+2ab+b²+ab
=(a+b)²+ab
=5²+6
=25+6
=31