A seguence exercise. Find an and n if given Sn, a1 and d. Sn=80, a1=2, d=7
Answers
Answered by
0
Answer:
n=5
an=37
Step-by-step explanation:
a1=2
d=7
Sn=n/2[2a1+(n-1)d]
80=n/2[4+7n-7]
160=n[-3+7n]
160=-3n+7n²
7n²-3n-160=0
n=5 or n=-32/7
now n is always positive so the value of n is 5
now to find an
an=a1+(n-1)d
an=2+5×7
an=37
please make my answer brainliest
Similar questions