Question

X+2X+3X+...........+50X-1260X=90


E CU SUMA LUI GAUSS


PLS

Answer 1

1+2+3+...+n=n*(n+1):2

x+2x+3x+....+50x-1260x=90
x*(1+2+3+...50)-1260x=90
[x*50*51:2]-1260x=90
x*1275-1260*x=90
x*(1275-1260)=90
x*15=90
x=90:15
x=6