an=an-1-2an-2, n>=3. Given that a4=-12, a3=0. What is the value of a1? (note : subscripts are provided in bold)
a)3
b)4
c)5
d)6
e)8
a)3
b)4
c)5
d)6
e)8
in first find a2
a4 = a3 - 2*a2
so a2 = (a3-a4)/2
after that find a1
