Question

For an A.P. T3=7 T4=3. Find the first term​

Answer 1

Answer:

15

Step-by-step explanation:

Let the 3rd term of A.P be a₃ and 4th be a₄

As we know, for the nth term of any A.P,

$a_{n-1} + d = a_n$

where, d is the common difference

d = $a_n - a_{n-1}$

d = a₄ - a₃

d = 3 - 7 = -4

From the equation for nth term of an A.P,

$a_n = a + (n-1)d$

where a is the first term

a₃ = a + 2d

7 = a - 8

a = 15

Answer 2

Answer:

Step-by-step explanation:

A3=7

a+2d=7

a=7-2d →1equation

Again,

A4=3

a+3d=3

(7-2d)+3d=3 [from eq.1]

7-2d+3d=3

d=-4

Putting value of d in A4 we get,

a+3(-4)=3

a-12=3

a=15

Therfore first term is 15