问题
填空题
设数列{an},{bn}都是等差数列.若a1+b1=7,a3+b3=21,则a5+b5=________.
答案
35
因为{an},{bn}都是等差数列,所以也成等差数列,根据等差数列的性质,a1+b1=7,a3+b3=21, a5+b5成等差数列,因而a5+b5=
.
设数列{an},{bn}都是等差数列.若a1+b1=7,a3+b3=21,则a5+b5=________.
35
因为{an},{bn}都是等差数列,所以也成等差数列,根据等差数列的性质,a1+b1=7,a3+b3=21, a5+b5成等差数列,因而a5+b5=
.