Question

Tentukan nilai x, jika (2x+1) + (2x + 2) + (2x + 3) + ....... + (2x + 50) = 4275

Answer 1

(2x+1)+(2x+2)+(2x+3)+......+(2x+50) = 4275
50(2x) + 1+50 . 25 = 4275
100x + 1275 = 4275
x = 4275 - 1275 / 100
x = 3000 / 100
x = 30

Answer 2

A=U1=2x+1
U2=2x+2
b=U2-U1=2x+2-(2x+1)=1
Un=a+(n-1)b
=2x+1+(n-1)1=2x+50
2x+n=2x+50
n=50
Sn=n/2(a+Un)
=50/2(2x+1+(2x+50))=4275
=25(4x+51)=4275
=100x+1275=4275
=100x=3000
x=30