设a.b都表示数,规定:a*b=3a+2b.式计算:⑴(5*6)*7 ⑵5*(6*7)

问题描述:

设a.b都表示数,规定:a*b=3a+2b.式计算:⑴(5*6)*7 ⑵5*(6*7)

⑴(5*6)*7
=(3x5+2x6)*7
=27*7
=3x27+2x7
=95
⑵5*(6*7)
=5*(3x6+2x7)
=5*32
=3x5+2x32
=79