若一组按规律排成的数为:3,8,-15,24,35,-48,63,80,-99……,则这组数的第3n+1项是
问题描述:
若一组按规律排成的数为:3,8,-15,24,35,-48,63,80,-99……,则这组数的第3n+1项是
答
若一组按规律排成的数为:3,8,-15,24,35,-48,63,80,-99……,则这组数的第3n+1项是