已知a+b=5,ab=3,求3a-5ab+3b-4的值
问题描述:
已知a+b=5,ab=3,求3a-5ab+3b-4的值
答
a+b=5,ab=3,
3a-5ab+3b-4
=3(a+b)-5ab-4
=3×5-5×3-4
=-4