the seventeenth term of an ap is 5 morethan twice its eighteenth term . If the 11 term of the ap is 43 find its nth term
Answers
Answered by
10
Answer:
nth term = 109 - 6n
or
103 - 6(n-1)
Step-by-step explanation:
nth term of an ap = a + (n-1)d
17th Term = a + (17-1)d = a + 16d
18th term = a + (18-1)d = a + 17d
17th term = 2 * (18th term) + 5
a + 16d = 2 * ( a+ 17d) +5
a +16d = 2a + 34d + 5
a + 18d = - 5 Eq 1
11th term = a + (11-1)d = a + 10d
a + 10d = 43 Eq 2
Eq 1 - Eq 2
8d = -48
d = -6
a + 10(-6) = 43
a = 103
nth rem = 103+ (n-1)(-6)
= 103 - 6(n-1)
= 103 - 6n + 6
= 109 - 6n
Answered by
23
a17 = a+16 d
a18 = a+17 d
a17 = 5 + 2 × a18
a+16d = 5+ 2(a+17 d)
a+16 d = 5+2a+34d
16d-34d -5 =2a-a
a11 =43
a+10d = 43
-18d -5 +10d =43
-8d -5 =43
-8d =43+5
-8d =48
a=-18 d -5
a= -18×-6 -5
a= 108 -5
an = 103 + (n-1) × -6
an =103 -6n +6
a18 = a+17 d
a17 = 5 + 2 × a18
a+16d = 5+ 2(a+17 d)
a+16 d = 5+2a+34d
16d-34d -5 =2a-a
a11 =43
a+10d = 43
-18d -5 +10d =43
-8d -5 =43
-8d =43+5
-8d =48
a=-18 d -5
a= -18×-6 -5
a= 108 -5
an = 103 + (n-1) × -6
an =103 -6n +6
SillySam:
Hehehe.... thnx... xD ❤☺
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