Question

The 4th term of an AP is zero.Prove that the 25th term of the AP is three times its 11th term.​

Answer 1

Let a be the first term and d be the common difference of an A.P.

And no. of terms as “n”

We know that

An = a + ( n − 1 ) d

ATQ

A4 = a + 3d = 0

a = - 3d

Need to prove that

A25 = a + 24d = 3( a + 10d)

A25 =−3d+24d

A25 = 21d------ (1)

A11 =a+10d

A11 =−3d+10d

A11 = 7d---- (2)

From equation (1) and (2), we get

A25 =3A11

Hence proved.

Answer 2

Answer:

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