Answer
Finite sequence: $1 + 3 + 5 + 7 + 9 + 11 + 13 + 15$
Total number of shrubs: 64 shrubs
Work Step by Step
1 in 1st row, 3 in 2nd row, 5 in 3rd row
$3-1=2$
$5-3=2$
This is an arithmetic sequence with $a_1=1$, $n=8$, and $d= 2$
$a_n=a_1 + (n-1)*d$
$a_8 = a_1 + (n-1)*d$
$a_8 = 1 + (8-1)*2$
$a_8 = 1+ 7*2$
$a_8 = 1+14$
$a_8 = 15$
We can use the $S_n$ formula to find the sum of the finite sequence.
$S_n = (n/2) * (2a+(n-1)*d)$
$n=8$
$a=1$
$d=2$
$S_n = (n/2) * (2a+(n-1)*d)$
$S_8 = (8/2) * (2*1+(8-1)*2)$
$S_8 = 4*(2+7*2)$
$S_8=4*(2+14)$
$S_8 = 4*16$
$S_8=64$
