a*b=2 a+b=3.求3a²+3b²的值

a*b=2 a+b=3.求3a²+3b²的值
a*b=2 a+b=3.求3a²+3b²的值

a*b=2 a+b=3.求3a²+3b²的值
3a²+3b²
=3（a²+b²）
=3【（a+b）²-2ab】
=3×（3²-2×2）
=15

3a²+3b²
=3[(a+b)²-2ab]
=3(9-4)
=15

3a²+3b²
=3(a²+b²)+6ab-6ab
=3(a²+b²+2ab)-6ab
=3(a+b)²-6ab
=3*3²-6*2
=27-12
=15

3a²+3b²=(根号3*a+根号3*b)²-6*a*b=[根号3(a+b)]²-6*a*b
下面带入就好了~~
同学~好好学习啊~~