Question

Tentukan jumlah dari 10 suku pertama padma deret aritmetika berikut
a.2+7+12+17...
b.6+10+14+18....
c.50+45+40+35...
d.1/2+1+3/2+2+...

Answer 1

Soalan a
Un = a+(n-1)b
U10 = 2 +(10-1)5
U10 = 2 + (9x5)
U10 = 2 + 45
U10 = 47
maka,
S10 = 10/2 (2+47)
S10 = 5 (49)
S10 = 245

soalan b
Sn = n/2 (2a+(n-1)b)
S10 = 10/2 (2x6 +(10-1)4)
S10 = 5 (12 + (9x4)
S10 = 5 (12 + 36)
S10 = 5 x 48
S10 = 240

soalan c
Sn = n/2 (2a+(n-1)b)
S10 = 10/2 (2x50 +(10-1)-5)
S10 = 5 (100 +(9x-5)
S10 = 5 (100 + -45)
S10 = 5 (55)
S10 = 275

soalan d
S10 = 10/2 (2x0,5 + (10-1)0,5)
S10 = 5 (1+ (9x0,5)
S10 = 5 (1+4,5)
S10 = 5(5,5)
S10 = 27,5