挑战习题
1/3单选题
难度:

1.已知等比数列{an},则下列一定是等比数列的是(  )
A {an+an+1}
B
C {an+2}
D {|an|}
提示1:
IOWIqeeUqOetieavlOaVsOWIl+eahOWumuS5iQ==
正确答案:RA==
6Kej77ya6Kej77ya4oi1PGltZyB3aWR0aD01NiBoZWlnaHQ9NDYgc3JjPSJodHRwczovL3AyLnFpbmdndW8uY29tL0cxL00wMC9GRS83OC9yQkFDRTFOUXVtZVM4MEx4QUFBQ1dCNDBsemc1MjIucG5nIj7kuLrluLjmlbDvvIw8YnI+4oi0PGltZyB3aWR0aD02NiBoZWlnaHQ9NTAgc3JjPSJodHRwczovL3AyLnFpbmdndW8uY29tL0cxL00wMC9GRS83OC9yQkFDRTFOUXVtZUFLN0xKQUFBQ2xyT0c0clU4ODQucG5nIj7kuZ/kuLrluLjmlbDvvIw8YnI+4oi05pWw5YiXe3xhPHN1Yj5uPC9zdWI+fH3kuIDlrprmmK/nrYnmr5TmlbDliJcuIDxicj7mlYXpgIlELiA=