If 7 times the 7th term of an A.P is equal to 11 times its 11th term, then find its 18th term
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Answered by
18
7*a7=11*a11
7(a+6d)=11(a+10d)
7a+42d=11a+110d
11a-7a+110d-42d=0
4a+68d=0
4(a+17d)=0
a+17d=0
a18=0
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7(a+6d)=11(a+10d)
7a+42d=11a+110d
11a-7a+110d-42d=0
4a+68d=0
4(a+17d)=0
a+17d=0
a18=0
......hope this helps you!!
please mark me brainliest
Answered by
2
given :-
7 ( a7 ) = 11 ( a11 )
7 ( a + 6d ) = 11 ( a + 10d )
7a + 42d = 11a + 110d
7a - 11a + 42d - 110d = 0
4a - 68d = 0
a - 17d = 0
a = 17d .... ( i )
To find 18th term
a18 = a + ( n - 1 )d
a18 = a + 17d
a18 = 17d + 17d
a18 = 34d
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