Question

Help me plz will fan and medal!
Write a recursive rule for the sequence.
a^n = −9+ 2n
a. a^1 = −9,a^n = a^n − 1 − 9
b. a^1 = −9,a^n = a^n − 1 + 2
c. a^1 = −7,a^n = a^n − 1 − 9
d. a^1 = −7,a^n = a^n − 1 + 2

Answer 1

I eliminated C and D.

Answer 2

d is the correct answer

Answer 3

How?? @Saurabh135

Answer 4

see if we put n=1 in above equation,
then a^1 will be equal to -9+2*1 = -7

Answer 5

and if we put n-1 instead of n in above equation then
a^n-1 = -9 + 2*(n-1)
= -9 + 2n -2
and subtracting these equations we get
a^n - a^n-1 = 2
which implies a^n = a^n-1 + 2