Question

求过程解答！！

Answer 1

 

追答

B

是A

a1,a3,a4成等比数列 a3^2=a1*a4 a3^2=(a3-2d)*(a3+d) a3^2=a3^2-2d^2-d*a3 d*(2d+a3)=0 d1=0 d2=-a3/2 d=0时 (s3-s2)/(s5-s3) =a3/(a4+a5) =1/2 d=-a3/2时 (s3-s2)/(s5-s3) =a3/(a4+a5) =a3/(2a3-3a3/2) =1/(1/2)=2

不容易。谢谢您