Question

Piz help me out with this one

Answer 1

Answer: -2n+9

This is because the starting value is 9, so it has to be included in the equation. 

Answer 2

hello : 
the formula is : an = a1+(n-1)d        a1 : the first term       d : is the common diff
an = 9+(n-1)(-2)
 an =9-2n+2
an = -2n +[ 11 ]