Question

The sum of n terms of an arithmetic sequence with first term 3 and common difference 4 is 1830. Calculate the value of n

Answer 1

My working out: S1830 =n/2 (2x3+(n-1)x4)
1830 = 2n (6+ n x4)
n = 1830/2 x 24

Answer 2

but i got answer completely wrong lol

Answer 3

re-check your second step..

Answer 4

\[Sn = \frac{ n }{ 2 } \times ( 2a + (n-1)d)\]

\[1830 = \frac{ n }{ 2 } \times ( 2*3 + (n-1) 4)\]

Answer 5

n/2(2+4n)
n+2n^2 =1830
2n^2+n-1830=0

(2n+61)(n-30)=0

Answer 6

\[1830*2 = n(6 +4n -4)\]
\[3660 = n (4n +2)\]
\[3660 = 4n ^{2} + 2n\]
\[2n ^{2} + n - 1830 = 0 \]