Answer:
1) First term = -105/2
2) The first option is the correct answer 9/2[ 2 + 26]
Step-by-step explanation:
It is given that,
The first term of the arithmetic sequence in which.... a27=-1/2
and the common difference is 2
To find the First term
First term of an AP be a and common difference d the nth term can be written as,
an = a + (n-1)d
Here n = 27
d = 2 , a27 = -1/2
a + (26 x 2) = -1/2
a = -105/2
From the figure We get an = 3n - 1
To find first term a1 and ninth term s9
a1 = 3 x 1 - 1 = 2
a9 = 3x 9 - 1 = 26
Sum of nth term of an AP
n/2[first term + Last term]
first term a1 and Last term = 26
Sum of first 9 terms S9
S9 = 9/2[ 2 + 26]
First option is the correct answer
