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In an AP, if the common difference (d) = – 4, and the seventh term (a7) is 4, then find the first term.

2 Answers

+1 vote
by (83.1k points)
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Best answer

a + 6 (–4) = 4

⇒ a = 28

Detailed Answer :

Given d = – 4 and a7 = 4

We know that nth term of A.P. is

an = a + (n – 1)d

a7 = a + (7 – 1)d      [n = 7]

4 = a + 6(– 4)

∴ a = 4 + 24 = 28 

∴ First term of an A.P. = 28.

+1 vote
by (11.0k points)

n th term an = a1+ (n-1)d

a7 = a1+( 7-1)* (-4)

=> 4 = a1+( 7-1)* (-4)

=> a1= 4-+24 =28

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