ada yang bisa bantu?

a = k+1/k
b = u2 - u1 = k+3/k - k+1/k = 2/k

Sn = n/2(2a +(n-1)b)
Sn = n/2( 2((k+1)/k) + (n-1)2/k)
Sn = n/2(2k+2/k + 2n-2/k)
Sn = n/2(2k+2n/k)
Sn = n/2 (2(n+k)/k)
Sn = 2n/2 (n+k/k)
Sn = n/k (n+k)

jawabannya yg C