(vi) given a=2, d=8, S =90, find n and a
Answers
Answered by
0
Answer:
Step-by-step explanation:
now, S = n/2 (2a + (n-1)d)
90 = n/2 (4 + 8n - 8)
180 = n (8n -4)
8n^2 - 4n - 180 = 0
2n^2 - n - 45 = 0
2n^2 - 10n + 9n - 45 = 0
2n(n-5) + 9 (n-5) = 0
=(2n−9)(n−5)
n=5 or 9/2 (but n is a +ve integer, so cant be 9/2)
a =a+(n−1)d
a =2+(5−1)8
a =2+32
a =34
hope it did helped
please mark as brainliest if it did
Answered by
0
Answer:
Step-by-step explanation:
Attachments:
Similar questions