Question

If the first term of an AP is 7 and the 7 term is 19,
then find its 18th term? I need step by step explanation. ​

Answer 1

Answer:

18

= 0.

Step-by-step explanation:

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▶ Given :-

→ 7a_7a

7

= 11a_{11}a

11

▶ To prove :-

→ a_{18}a

18

= 0 .

$\huge \green{ \underline{ \overline{ \bf Solution :- }}} </p><p>$

We have,

=> 7a_7a

7

= 11a_{11}a

11

=> 7( a + 6d ) = 11( a + 10d ) .

=> 7a + 42d = 11a + 110d .

=> 11a - 7a = 42d - 110d .

=> 4a = - 68d .

=> 4a + 68d = 0 .

=> 4( a + 17d ) = 0 .

=> a + 17d = 0/4 .

=> a + ( 18 - 1 )d = 0.

$\huge \boxed{ \boxed{ \blue{ \bf\therefore a_{18} = 0.}}}$

∴a

18

=0.

✔✔ Hence, it is proved

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Answer 2

Step-by-step explanation:

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