Question

solve the following sum plzz​

Answer 1

Answer:

a=-8d

now t29=a+28d

-8d+28d

=20d

Answer 2

Answer:

Now, By using nth term of an A.P. formula

tn = a + (n – 1)d

where n = no. of terms

a = first term

d = common difference

tn = nth terms

Given: t9 = 0

⇒ t9 = a + (9 – 1)d

⇒ 0 = a + 8d

⇒ a = – 8d

To Show: t29 = 2× t19

Now,

⇒ t29 = a + (29 – 1)d

⇒ t29 = a + 28d

⇒ t29 = – 8d + 28d = 20 d (since, a = – 8d )

⇒ t29 = 20 d

⇒ t29 = 2 × 10 d ….(1)

Also,

⇒ t19 = a + (19 – 1)d

⇒ t19 = a + 18d

⇒ t19 = – 8d + 18d = 10 d (since, a = – 8d )

⇒ t19 = 10 d …..(2)

From eq. (1) and eq. (2) we get,

t29 = 2× t19.

Step-by-step explanation:

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