156009是四个连续奇数的积,求他们的和
问题描述:
156009是四个连续奇数的积,求他们的和
答
(2x-3) (2x-1) (2x+1) (2x+3)=156009 (4x^2-1)(4x^2-9)=156009令x^2=t得(4t-1)(4t-9)=15600916t^2-40t+9=15600916t^2-40t=1560004t^2-10t=39000(2t-2.5)^2=39006.25t=100x=10所以这4个连续奇数的和为80