已知-2,b1,b2,b3,-32成等比数列,-2,a1,a2,a3,-32成等差数列,求(a3-a1)*b2
问题描述:
已知-2,b1,b2,b3,-32成等比数列,-2,a1,a2,a3,-32成等差数列,求(a3-a1)*b2
答
啥啊,数学题都上来了,牛!
答
(b2)^2=-2*(-32) ,b2=-2q^2=-8,-32=-2+4d,d=-7.5 (a3-a1)*b2=-2d*(-8)=-120