Answer:
tn = 8n -7
Step-by-step explanation:
given : t2=9, t4=25
the formula is:
tn = t1 + (n-1) d
gonna find d first:
d = (25-9) /(4-2) = 16/2 = 8
and find tn1:
t1 = 9-8 = 1
so, tn = 1 + (n-1) (8) = 1 +8n -8
Solution given
n th term[tn]=?
1st term =a
difference =d
we have
t2=9
a+(n-1)d=9
a+(2-1)d=9
a+d=9
a=9-d..................[1]
again
t4=25
a+(n-1)d=25
a+(4-1)d=25
now
substituting value of a
9-d+3d=25
2d=25-9
d=16/2
d=8
substituting value of d in equation 1.
,a=9-8
a=1
tn term =a+(n-1)d=1+(n-1)8=1+8n-8=8n-7
n th term =8n-7
