The answer is 0.
The expression in algebraic form is :
We know subtracting a term from its equivalent term will be 0.
Hello :
by : <span>an = an-1 + 9.
n= 2 : a2 =a1+9
a2 = -12+9 = -3
n=3 : a3 = a2 +9
a3 = -3+9 = 6
n = 4 : a4 = a3 +9
a4 =6+9 = 15</span>
There is little context to go off of but the answer should be variable
The answer should be 2.12