Given
[tex]4x^2+2x-5[/tex]
Divide it by (x+1) using synthetic division, as shown below
The green line is a minus sign.
Thus,
[tex]\Rightarrow4x^2+2x-5=(x+1)(4x-2)-3[/tex]
Therefore, since the remainder is different than zero, (x+1) is not a factor of 4x^2+2x-5
