50a1+d(1+3+5+`````+99)=80
没问题
50a1+d(1+99)*50/2=80
50a1+1/2*100*50/2=80
50a1=80-1250
a1=-23.4可我算出的a1=-22.9啊你算错了呗50a1+d(1+3+5+`````+99)=8050a1+2450d=8050a1+1225=8050a1=-1145a1=-22.9我哪里错了？1+3+5+`````+99=2500