Question

If the forth term of an arithemetic progression is 14 and 12the term is 70. then the first term is?

Answer 1

$a_{n} = a + (n - 1)d$
$a_{4}= a+(4-1)d$
$a_{12}=a+(12-1)d$

14=a+3d...................(1)
70=a+11d..................(2)
by using elimination method we get,
d=7
on substi. the value of d in eq (2)
14= a+ 3×7
14= a+21
14-21= a
a=-7

Answer 2

hello.


if the 4th term of an A.P. IS 14 AND 12TH term is 70 then the 1st term will be -7.


hope helps uh