(6/1+7/1+8/1)x(7/1+8/1+9/1)-(6/1+7/1+8/1+9/1)x(7/1+8/1)
根据数据特点,假设:7/1+8/1+9/1=b,7/1+8/1=a
b-a=7/1+8/1+9/1-7/1-8/1=9/1
则:上式=(6/1+a)x b-(6/1+b)x a
=(6/1×b+ab)-(6/1×a+ab)
=6/1×b+ab-6/1×a-ab
=6/1×(b-a)
=6/1×9/1
=54/1
(6/1+7/1+8/1)x(7/1+8/1+9/1)-(6/1+7/1+8/1+9/1)x(7/1+8/1)
根据数据特点,假设:7/1+8/1+9/1=b,7/1+8/1=a
b-a=7/1+8/1+9/1-7/1-8/1=9/1
则:上式=(6/1+a)x b-(6/1+b)x a
=(6/1×b+ab)-(6/1×a+ab)
=6/1×b+ab-6/1×a-ab
=6/1×(b-a)
=6/1×9/1
=54/1