The remainder theorem states that when a polynomial is divided by a binomial, the value that makes the binomial equal 0 can be substituted into the polynomial to obtain the remainder.
In other words, we can plug in 1 into the polynomial, as (1 - 1) = 0
4(1)^3 + 4(1)^2 + 2(1) + 3 =
4 + 4 + 2 + 3 = 13
As the polynomial equals 13, the remainder when the polynomial is divided is 13/(x -1), so it’s NOT a factor of the polynomial.
If the remainder were 0, then (x - 1) WOULD be a factor of the polynomial, but it’s not.
To sum it up, the remainder is 13/(x - 1), and the binomial is NOT a factor of the polynomial.