Question 139
What is the first term of the sequence given recursively by the formula $a_{n}=2 a_{n-1}+1$, if the fifth term equals $7$?
(A) $2$
(B) $15$
(C) $-\frac{7}{2}$
(D) $-\frac{1}{2}$
(E) $-5$
(A) $2$
(B) $15$
(C) $-\frac{7}{2}$
(D) $-\frac{1}{2}$
(E) $-5$