First term of an arithmetic sequence is 28 and common difference is 4. a) Write the arithmetic sequence. b) Find it's 8th term. c) What is sum of its first 15 terms. d) What is the sum of the first 15 terms of the arithmetic sequence -28,-24,-20,...
Answers
Answer:
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Answer:
a)28,32,36,40,44,..........
b)56
c)840
d)0
Step-by-step explanation:
a)SOLUTION:
GIVEN:
a=28,d=4
ARITHMETIC SEQUENCE:
28,32,36,40,44,.....................
b)SOLUTION:
GIVEN:
a=28,d=4,n=8
tn=a+(n-1)d
=28+(8-1)4
=28+(7)4
=28+28
tn=56
c)SOLUTION:
Sn=n(a+l)/2
l=a+(n-1)d
=28+(15-1)4
=28+56
l =84
Sn=15(28+84)/2
=15(112)/2
=1680/2
Sn =840
d)SOLUTION:
GIVEN:
a=-28,d=[-24-(-28)], n=15
=[-24+28]
=4
l=a+(n-1)d
=-28+(15-1)4
=-28+56
l =28
Sn=n(a+l)/2
=15(-28+28)
=15(0)
Sn=0