Perfect Square Trinomials
Before we can get to defining a perfect square trinomial, we need to review some vocabulary.
Perfect squares are numbers or expressions that are the product of a number or expression multiplied to itself. 7 times 7 is 49, so 49 is a perfect square. x squared times x squared equals x to the fourth, so x to the fourth is a perfect square.
Binomials are algrebraic expressions containing only two terms. Example: x + 3Trinomials are algebraic expressions that contain three terms. Example: 3x2 + 5x - 6Perfect square trinomials are algebraic expressions with three terms that are created by multiplying a binomial to itself. Example: (3x + 2y)2 = 9x2 + 12xy + 4y2Recognizing when you have these perfect square trinomials will make factoring them much simpler. They are also very helpful when solving and graphing certain kinds of equations.The Square of a BinomialWith perfect square trinomials, you will need to be able to move forwards and backwards. You should be able to take the binomials and find the perfect square trinomial and you should be able to take the perfect square trinomials and create the binomials from which it came. Any time you take a binomial and multiply it to itself, you end up with a perfect square trinomial. For example, take the binomial (x + 2) and multiply it by itself (x + 2).(x + 2)(x + 2) = x2 + 4x + 4The result is a perfect square trinomial.To find the perfect square trinomial from the binomial, you will follow four steps:Step One: Square the aStep Two: Square the bStep Three: Multiply 2 by a by bStep Four: Add a2, b2, and 2ab(a + b)2 = a2 + 2ab + b2Let's add some numbers now and find the perfect square trinomial for 2x - 3y. For this:a = 2x
b = 3yStep One: Square the a
a2 = 4x2Step Two: Square the b
b2 = 9y2Step Three: Multiply 2 by a by 'b
2(2x)(-3y) = -12xyStep Four: Add a2, b2, and 2ab
4x2 - 12xy + 9y