Question

(x-1)/2+(x-2)/2+(x-3)/2+...(x-100)/2=...

Answer 1

(x-1)/2+(x-2)/2+(x-3)/2+...(x-100)/2

1/2 (x-1 + x-2 + x-3 + ... + x-100)
= 1/2 (x+x+x... - (1+2+3..+100))
= 1/2 (100x - 100*101/2)
= 50x - 2525