Question

Tentukan Nilai x,jika (2x+1)+(2x+2)+(2x+3)+...+(2x+50)=4.275

Answer 1

Jumlahkan konstantanya:
1 + 2 + ... + 50   = a
50 + 49 + ... + 1 = a
_________________ +
51 x 50 = 2a
a = 51 x 25 = 1275

50(2x) = 100x
maka:
100x + 1275 = 4275
100x = 3000
x = 30

Answer 2

    Sn = n/2 ( 2a + ( n - 1 ) b )
4.275 = 25 ( 2(2x+1) + 49 )
4.275 = 25 ( 4x + 51 )
4.275 = 100x + 1.275
 100x = 3.000
       x = 30