15÷5×(-3)-6÷( )...①
=15÷(-15)-(4-9)......... ②
=-1+5.................................... ③
=4.......................................... ④
1*3=1×5+3=8;3*(-1)=3×5-1=14;5*4=5×5+4=29;
4*(-3)=4×5-3=17
请你算一算:(-3)*(-6)=
请你想一想:a*b=
若a*(-b)=5,请计算(a-b)*(5a+3b)的值.