Question

Find the first term and 20th term of an A.P. whose 5th of 7th term due 13 and 17
respectively.
(a) 5, 45
3.42
(c)
(d)
3,45
(b) 5,43​

Answer 1

Answer:

Option b) 5, 43 is the answer.

Step-by-step explanation:

It is given that,

a5 = 13                    and            a7 = 17

Therefore,

a5 = a  + 4d  = 13   -eqn1

a7 = a + 6d = 17       -eqn2

Subtracting eqn 1 from 2,

2d = 4  

thus, d = 2.

Now substituting, 2 in eqn 1,

a = 5.

Therefore,  first term ( a ) = 5.

Now 20th term = a + 19d

                         = 5 + 19(2) = 43.

Thus, a1 = 5 and a20 = 43

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