【单选题】______ birds use their feathers for flight, some of their feathers are for other purposes.
【单选题】已知在等比数列{ }中, , ,则等比数列{ }的公比q的值为( )
【简答题】已知等差数列 中,已知首相 ,公差 ( 1 )求等差数列 的通项公式 , 和 ; ( 2 )求等差数列 的前 20 项和 . ( 3 )在正项等比数列 中,已知 , ,求 等比数列 的公比 q .
【简答题】在等比数列{ a n }中, a n >0,且 a n + 2 = a n + a n + 1 ,则该数列的公比 q = .
【单选题】在等比数列 中, ,公比q=2 , 则 ( ) , ( )
【单选题】在等比数列{a n }中,a 5 、a 4 、a 6 成等差数列,则公比q等于( )
【单选题】What do the fishermen do to encourage the birds?
A.
They use a long string to beat the birds.
B.
They give the birds some fish to encourage the birds.
C.
They beat the sides of the boat to stimulate the birds.
D.
They grasp several birds in one hand.