化简求值:3(x2+xy)-2(x3-y3-3xy)+(-3xy-2y3),其中x=1,y=2

题目

化简求值:3(x2+xy)-2(x3-y3-3xy)+(-3xy-2y3),其中x=1,y=2

答案

=x6+3xy-x6+y6+6xy-6xy-6y
=(6-6)x+(3+6)xy+y6-6y
=9xy+y6-6y
因：x=1 y=2
所：9xy+y6-6y
=9*1*2+2*6-6*2
=18+12-12
=18