[tex]ax^2 + 3x + c = 0[/tex]
if a = 2c and zero is the remainder when divided by x+1.
using remainder's theorem, we will plug in the value of x as
x+1 = 0
x = -1
[tex]ax^2 + 3x + c = 0[/tex]
[tex]a(-1)^2 + 3(-1) + c = 0[/tex]
[tex]a - 3 + c = 0[/tex]
since a = 2c
[tex]2c - 3 + c = 0[/tex]
[tex]3c = 3[/tex]
[tex]c = 1[/tex]
substitute c = 1 to a=2c
[tex]a = 2c[/tex]
[tex]a = 2(1)[/tex]
[tex]a = 2[/tex]