How do you use the factor theorem to determine whether x-1 is a factor of #f(x)=x^3+4x-5#? Precalculus Real Zeros of Polynomials Remainder and Factor Theorems 1 Answer Topscooter Jan 6, 2016 Calculate #f(1)#. Explanation: If #f(1) = 0#, then #x - 1# is a factor of #f#. So let's calculate #f(1)#. #f(1) = 1 + 4 - 5 = 5 - 5 = 0#. So #1# is a root of this polynomial, and #x - 1# is a factor of it. Answer link Related questions What is the remainder theorem? What is the factor theorem? What does the remainder theorem mean? What does the factor theorem mean? How are the remainder and factor theorems useful? How do I use the remainder theorem to evaluate polynomials? How do I use the remainder theorem to divide #2x^2-5x-1# by #x-3#? How do I use the remainder theorem to divide #2x^2-5x-1# by #x-4#? How do I use the factor theorem to prove #x-2# must be a factor of #2x^3-x^2-7x+2#? How do I use the factor theorem to prove #x-4# must be a factor of #x^2-3x-4#? See all questions in Remainder and Factor Theorems Impact of this question 2146 views around the world You can reuse this answer Creative Commons License