Answer:
NO, 12 is not the fifth term in the sequence
Step-by-step explanation:
Given the sequence of 10 terms:
First term a1 = 1
second term a2 = x
third term a3 = a2+a1
Since each term after the second is the sum of the previous two terms then;
a3 = x+ 1
a4 = a3 + a2
a4 = x+1+x
a4 = 2x+1
Also
a5 = a4+a3
a5 = 2x+1+x+ 1
a5 = 3x+2
Get x:
The common difference d = a2-a1 = a3-a2
d = x-1 = x+1-x
x-1 = x+1-x
x-x+x = 1+1
x = 2
Get the fifth term:
Recall that a5 = 3x+2
a5 = 3(2)+2
a5 = 6+2
a5 = 8
Hence the fifth term of the sequence is 8 not 12
