Help! Medals awarded! For the sequence an=4n+5 Find the sum of the first 9 terms

Question

anonymous · Answer

i need some serious help from anyone willing to try

ikram002p · Answer

ok its easy locate n from 1,...,9
now u need to find a1,.....,a9
i'm gonna solve a1 & a2 and u try wid the rest of them
a1=4(1)+5=4+5=1
a2=4(2)+5=8+5=13
got it or still confused ??

magbak · Answer

@werty00

anonymous · Answer

I'm still kinda confused..

ikram002p · Answer

sry i thought u wanna the first 9 turms not the sum , ok to find the sum 
$$\sum_{1}^{9}4n+5$$
=$$ 4 \sum_{1}^{9}n + (5\times (9-1))$$
do u know this formula ??

anonymous · Answer

432

anonymous · Answer

the formula is SUM = n/2 * (2a1 + (n-1) * d) = 9/2 * (2*1 + (9-1) * 12)

ikram002p · Answer

i think the answer 184 at the end