已知等比[an]中an>0,a1和a99是方程X²-10X+16=0的两根,则a40×a50×a60=?
问题描述:
已知等比[an]中an>0,a1和a99是方程X²-10X+16=0的两根,则a40×a50×a60=?
答
a40×a50×a60=a50^3 a1a99=a50^2=a16 an>0 a50=4 a40×a50×a60=a50^3=4^3=64