根据题意得:a-b-3=0b+1=0,
解得:a=2b=-1,
则ab=12.
故答案是:12.
My brother has a ______ daughter. She’s kind and lovely.
A.four-years-old
B.four-year-old
C.fourth-year-old
D.four-year-olds
条码阅读器通过条码符号中()实现识读
A、特定标识
B、标签与数字符
C、条与空对光反射率的对比
D、光电反映