a) If 5th and 9th term of Ap are 44 and 68 calculate the sum of first 25th term
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Answer:
3500
Step-by-step explanation:
A5=44
a+4d = 44 ____eq.1
A9 =68
a+8d = 68 _____eq.2
subtracting eq.1 from 2-
a+8d-a-4d=68-44
4d=24
d=12
put the value of d in eq.1
a+4×12=44
a+48=44
a=44-48
a=(-4)
a = -4 ,d = 12, n = 25
Sn=n/2(2a+(n-1)d
S25 = 25/2[2×(-4)+(25-1)×12]
S25=25/2[(-8)+24×12]
S25 = 25/2[(-8)+288]
S25 = 25/2×280
S25 =3500
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Answer:
sorry to say my brother.am extremely sorry
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