tentukan nilai y= x+13+x+23+x+33+....+x+1003

un = a+ (n-1) b
1003 = 8 + (n-1) . 5
1003 = 8 + 5n-5
1003-8 = 5n-5
995 = 5n
1000 = 5n
n =  1000/5
n= 200

Sn = 200/2 (2a+(n-1)b)
Sn = 100 (2.8 + 199.5
Sn = 100 (16 + 995)
Sn = 100 x 1011
Sn = 101100

misalkan y adalah deret, banyak x sama dgn n deret sehingga y=nx+Sn

a=U1=13
b=23-13=10
Un=1003

n=(Un-a+b)/b
n=(1003-13+10)/10
n=1000/10
n=100

Sn=n/2(a+Un)
S100=100/2(13+1003)
S100=50(1016)
S100=50800

y=nx+sn
y=100x+50800
y=100(x+508)