4 dg 6 ,no 6 yg pling pnting,pake cra yaa tolong makasihhh

4) (i = 1 Sigma 15) ai = 30
(i = 1 Sigma 15) (5ai + 6)
= 5 (i = 1 Sigma 15) ai + (i = 1 Sigma 15) 6
= 5 (30) + 6(15)
= 150 + 90
= 240

6) (n = 1 Sigma 50) [1/n - 1/(n + 1)]
= [1/1 - 1/2] + [1/2 - 1/3] + [1/3 - 1/4] + .... + [1/49 - 1/50] + [1/50 - 1/51]
= 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ....... + 1/49 - 1/50 + 1/50 - 1/51
= 1 - 1/51
= 50/51