已知a-b=5,ab=1,那么3a+(-3b)+(-6ab)=?速求!

问题描述:

已知a-b=5,ab=1,那么3a+(-3b)+(-6ab)=?速求!

3a+(-3b)+(-6ab)=3(a-b)-6ab=3*5-6*1=9

a-b=5
3(a-b)=15

,ab=1
6ab=6

3a+(-3b)+(-6ab)
=3a-3b-6ab
=15-6
=9

3a+(-3b)+(-6ab)
=3a-3b- 6ab
=3(a-b )-6ab
=3×5-6×1
=15-6
=9

3a+(-3b)+(-6ab)
=3(a-b)-6ab
=3×5-6
=9

3a+(-3b)+(-6ab)
=3(a-b)-6ab
=3×5-6×1
=15-6
=9