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Factoring Difference of Squares

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In some cases recognizing some common patterns in the trinomial or binomial will help you to factor it faster. For example, we could check whether the binomial is a difference of squares.

How to factor Difference of Squares?

A difference of squares is a binomial of the form:


Take note that the first term and the last term are both perfect squares.

When we factor a difference of two squares, we will get

a2b2 = (a + b)(a – b)

This is because (a + b)(a – b) = a2ab + ab – b2 = a2b2

Example: x2 – 25 = 0
  x2 – 52 = 0
  (x + 5)(x – 5) = 0

We get two values for x:

  x = -5, x = 5

Be careful! This method only works for difference of two squares and not for the sum of two squares:
a2 + b2 ≠ (a + b)(ab)

Example :

a) x2– 9
b) 4x2– 25
c) 2x2– 32
d) πR2πr2


a) x2– 9
= x2– 32
= (x + 3)(x – 3)

b) 4x2– 25
= (2x)2– (5)2
= (2x + 5)(2x – 5)

c) 2x2– 32
= 2(x2– 16)
= 2(x2 – 42)
= 2(x + 4)(x – 4)

d) πR2πr2
= π(R2r2)
= π(R + r)(R – r)

The following videos explain how to factor a difference of squares.


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