Polynomial Division (CIE A Level Maths: Pure 3)

What is a polynomial?

• A polynomial is an algebraic expression consisting of a finite number of terms, with non-negative integer indices only

 

What is polynomial division?

• Polynomial division is a method for splitting polynomials into factor pairs (with or without an accompanying remainder term)

• At A level you will most frequently use it to factorise polynomials, or when dealing with improper (ie 'top-heavy') algebraic fractions

How do I divide polynomials?

• The method used for polynomial division is just like the long division method (sometimes called 'bus stop division') used to divide regular numbers:

• At A level you will normally be dividing a polynomial dividend of degree 3 or 4 by a divisor in the form (x ± p)
• The answer to a polynomial division question is built up term by term, working downwards in powers of the variable (usually x)

• Start by dividing by the highest power term
• Write out this multiplied by the divisor and subtract

•  Continue to divide by each reducing power term and subtracting your answer each time

•  Continue until you are left with zero

• If the divisor is not a factor of the polynomial then there will be a remainder term left at the end of the division

What are the degrees of the quotient and remainder when a polynomial is divided by a quadratic divisor?

• Suppose a polynomial of degree is divided by a quadratic divisor
  • 
• The quotient q will have degree 
• The degree of the remainder r will be less than 
  • It could be degree 1 (linear)
  • Or it could be degree 0 (constant)

How do I divide a polynomial by a quadratic divisor?

• You use polynomial division!
• Step 1
  Divide the leading term of the polynomial by the squared term of the divisor
  • This gives the leading term of the quotient
• Step 2
  Multiply this term by the divisor
• Step 3
  Subtract this from the polynomial to get a new polynomial with a lower degree
• Continue these steps until you have an expression with a degree lower than 2