问答题
【正确答案】正确答案:记y=(x 1 +x 2 )x 3 ,则e(y)=e((x 1 +x 2 )x 3 )=e(x 1 +x 2 )x 3 +(x 1 +x 2 )e(x 3 )=(e(x 1 )+e(x 2 ))x 3 +(x 1 +x
【答案解析】