what is factor theorem ?
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In algebra, the factor theorem is a theorem linking factors and zeros of a polynomial. It is a special case of the polynomial remainder theorem. The factor theorem states that a polynomial f(x) has a factor if and only if f(k)=0.
In mathematics, factor theorem is used when factoring the polynomials completely. It is a theorem that links factors and zeros of the polynomial.
According to factor theorem, if f(x) is a polynomial of degree n ≥ 1 and ‘a’ is any real number, then, (x-a) is a factor of f(x), if f(a)=0.
Also, we can say, if (x-a) is a factor of polynomial f(x), then f(a) = 0. This proves the converse of the theorem. Let us see the proof of this theorem along with examples.
Factor theorem is commonly used for factoring a polynomial and finding the roots of the polynomial. It is a special case of a polynomial remainder theorem.
As discussed in the introduction, a polynomial f(x) has a factor (x-a), if and only if, f(a) = 0. It is one of the methods to do the factorisation of a polynomial.
Here we will prove the factor theorem, according to which we can factorise the polynomial.
Consider a polynomial f(x) which is divided by (x-c), then f(c)=0.
Using remainder theorem,
➡f(x)= (x-c)q(x)+f(c)
Where f(x) is the target polynomial and q(x) is the quotient polynomial.
➡Since, f(c) = 0, hence,
➡f(x)= (x-c)q(x)+f(c)
➡f(x) = (x-c)q(x)+0
➡f(x) = (x-c)q(x)