Problem: The first three terms of an arithmetic progression are x−1,x+1,2x+3, in the order shown. The value of x is:
Answer Choices:
A. −2
B. 0
C. 2
D. 4
E. undetermined
Solution:
Let d be the common difference
d=(x+1)−(x−1)=2, and
d=(2x+3)−(x+1)=x+2
∴x+2=2∴x=0
or
2(x+1)=(x−1)+(2x+3)
2x+2=3x+2
x=0