已知等差数列an是递增数列,且前三项依次是x^2-4x,-3/2,(x-1)^2-4,求x的值

问题描述:

已知等差数列an是递增数列,且前三项依次是x^2-4x,-3/2,(x-1)^2-4,求x的值
^2是平方的意思~~~~~~~~~~

(x-1)^2-4+x^2-4x=2*(-3/2)
2x^2-6x-3=-3
2x^2-6x=0
x^2-3x=0
x(X-3)=0
x=0舍去 x=3
x=3