Question

Tentukan nilai suku ke 32 dari barisan 1,3,6,10,15,21,...

Answer 1

Jawab:
Un   =1/2 x n x (n+1)
U32  = 1/2 x 32 x (32+1)
        = 16 x 33
        = 528

Answer 2

U1=1
u2=3 (2+1)
u3=6 (3+2+1)
u4=10 (4+3+2+1)
u5=15 (5+4+3+2+1)
u6=21 (6+5+4+3+2+1)
u32= 32+31+30+29+28+27+26+25+24+23+22+21=318 +20+19+18+17+16+15+14+13+12+11+10=483 +9+8+7+6+5+4+3+2+1=528