in an ap the 10thterm is 68 while it 4th term is 26 find the common different and the ist term

Answer 1

How about just using our definitons
"the 10thterm is 68" ----> a + 9d = 68
"the 4th term is 26 " ----> a + 3d = 26
subtract them:
6d = 42
d = 7
back in a + 3d = 26
a + 21 = 26
a = 5

btw, Its called common difference, not different.

Answer 2

six differences between 4th and 10th ... d = (68 - 26) / (10 - 4)

1st = 4th - 3 d