Question

For an AP if t4=20 and t7=32 find a,d and tn

​

Answer 1

t4 = 20

a + 3d = 20 ..........(I)

t7 = 32

a + 6d = 32........(II)

Solve both as linear equations

subtracting (II) from (I) ,

3d = 12

d = 4

a + 3d = 20

a = 20 - 12

a = 8

Put the values in the formula , an = a + ( n- 1 ) d....and you will get ur answer..... (•‿•)

Answer 2

Answer:

t4 = a + 3d , t7 = a + 6d

20 = a + 3d , 32 = a + 6d

by using elimination method

a + 3d = 20 — 1

a + 6d = 32

- - -

——————

- 3d = -12

d = 4

put value d in 1

a + 3×4 = 20

a + 12 = 20

a = 20-12

a = 8

hope it will help you