问题
解答题
化简后求值：（5a2-2b2+a2+2ab）-（+5a2-b2+2ab-3b2），其中a=2，b=3．
答案
原式=5a2-2b2+a2+2ab-5a2+b2-2ab+3b2
=5a2-5a2+a2-2b2+b2+3b2+2ab-2ab
=a2+2b2
∴原式=a2+2b2
=22+2×32
=4+2×9
=4+18=22．
搜题请搜索小程序“爱下问搜题”
化简后求值：（5a2-2b2+a2+2ab）-（+5a2-b2+2ab-3b2），其中a=2，b=3．
原式=5a2-2b2+a2+2ab-5a2+b2-2ab+3b2
=5a2-5a2+a2-2b2+b2+3b2+2ab-2ab
=a2+2b2
∴原式=a2+2b2
=22+2×32
=4+2×9
=4+18=22．