化简,求值：5a²-（3b²+7ab）+（2b²-5a²）,其中a=-0.1,b=0.2
问题描述：
化简,求值：5a²-（3b²+7ab）+（2b²-5a²）,其中a=-0.1,b=0.2
答
5a²-（3b²+7ab）+（2b²-5a²）
=5a²-3b²-7ab+2b²-5a²
=7ab-b²
当a=-0.1，b=0.2时
7ab-b²
=7×（-0.1）×0.2-0.2²
=-0.14-0.04
=-0.18
答
5a²-（3b²+7ab）+（2b²-5a²）
=5a²-3b²-7ab+2b²-5²
=-b²-7ab
=-(0.2)²-7×(-0.1)×(0.2)
=-0.04+0.14
=0.1
答
5a²-（3b²+7ab）+（2b²-5a²）
=5a²-3b²-7ab+2b²-5a²
=-b²-7ab
=-(0.2)²-7*(-0.1)*0.2
=-0.04+0.14
=0.1