(3.15+2.17+5.61)×(2.17+5.61+6.6)-(3.15+2.17+
1个回答

令3.15+2.17+5.61=x

令2.17+5.61=y

所以原式变成

x(y+6.6)-(x+6.6)y

=xy+6.6x-xy-6.6y

=6.6(x-y)

=6.6×[(3.15+2.17+5.61)-(2.17+5.61)]

=6.6×3.15

=20.79