Question

the fourth term of an ap is 7 and 9th term is 17 find its 15th term​

Answer 1

hey mate here is ur answer

《Solution》

Formula used = tn=a+(n-1)d

t4=a+3d

a+3d=7------(1)

t9=a+8d

a+8d=17-----(2)

Subtracting (2)-(1)

5d=10

d=2

a=17-16

a=1.

t15=a+14d

t15=1+14×2

=1+28

=29.

hence answer is 29.

hope it helps.

☆☆☆

Answer 2

Answer:

The 15th term of an A.P is 29 .

Step-by-step explanation:

Here is given,

:. t4= 7

:. a + (4–1) d = 7

:. a + 3d = 7 ----(1)

Then,

:. t9 = 17

:. a + 8d = 17

:. a + 3d + 5d = 17

:. 7 + 5d = 17 ----( from 1)

:. 5d = 10

:. d = 2

Put the value of d = 2 in equation 1, we get

:. a = 1

Let's find 15th term,

:. t15 = a + (n–1) × d

:. t15 = 1 + (15–1) × 2

:. t15 = 29

Hope it helps you !!

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