The fourth term of an ap is 1 less than twice the second term. If the sixth term is 7, find the first term.

Answer 1

Just translate into Math using your definitions of an AP
a+5d = 7 **

a+ 3d = 2(a+d) - 1
a + 3d = 2a + 2d - 1
-a + d = -1 ***

add ** and ***
6d = 6
d = 1
back in **
a + 5=7
a = 2

the first term is 2

check:
sequence is 2,3,4,5,6,7,8, ...
Is the fourth term less than twice the second by 1 ? YES
Is the 6th term equal to 7 ? YES
All is good.

Answer 2

The forth term of an A.P is one less than twice the 2nd term. If the sixth term is 7, find the first term

Answer 3

The first term is 2