TWO TERMS: DIFFERENCE OF SQUARES
TO BE FACTORABLE AN EXPRESSION WITH TWO TERMS MUST BE ONE OF THE FOLLOWING:
  • PERFECT SQUARE - PERFECT SQUARE
  • PERFECT CUBE - PERFECT CUBE
  • PERFECT CUBE + PERFECT CUBE
In this course, we only deal with the difference between two squares.
Recognizing terms that are perfect squares
Numbers: The square root of the number must be rational. The square root will be a whole number, a fraction,or a decimal that is repeating or terminating.
Letters with exponents: The exponent of the letter must be even.
Letters and numbers: Both must be perfect squares.

64 is a perfect square since it's square root is 8.
1/4 is a perfect square since it's square root is 1/2.
x8 is a perfect square since 8 is even.
x9 is not a perfect square since 9 is not even.
9x4 is a perfect square. (It's square root is 3x2)
3x2 is not a perfect square since 3 is not a perfect square.

 

Factoring the difference of two squares

If an expression is of the form perfect square - perfect square it will factor into two binomials that have the same terms but opposite signs between them.
To factor A2 - B2 the two binomials would be (A - B)(A + B)
The pattern will be the same for any perfect square minus perect square with the first positions being the square root of the first term and the second positions being the square root of the second term.
To factor 4x2 - 9y2 we will get (2x - 3y)(2x + 3y)