The GCF of an expression is a common factor of the terms in the expression. It is the common factor with the greatest coefficient and the greatest exponent. In this case, the GCF is 3.
The result of factoring out a GCF from the given expression is a trinomial with a leading coefficient of 1.
3( x^2-8x-9)
Let's temporarily only focus on this trinomial, and we will bring back the GCF after factoring.
Factor the Expression
To factor a trinomial with a leading coefficient of 1, think of the process as multiplying two binomials in reverse. Let's start by taking a look at the constant term.
x^2-8x - 9
In this case, we have -9. This is a negative number, so for the product of the constant terms in the factors to be negative',' these constants must have the opposite sign (one positive and one negative).
Constants
Product of Constants
1 and -9
-9
-1 and 9
-9
3 and -3
-9
Next, let's consider the coefficient of the linear term.
x^2 - 8x - 9
For this term, we need the sum of the factors that produced the constant term to equal the coefficient of the linear term, -8.
Constants
Sum of Constants
1 and -9
-8
-1 and 9
8
3 and -3
0
We found the factors whose product is -9 and whose sum is -8.
x^2 - 8x - 9 ⇔ (x+1)(x-9)
Wait! Before we finish, remember that we factored out a GCF from the original expression. To fully complete the factored expression, let's reintroduce that GCF now.
3(x+1)(x-9)
Checking Our Answer
Check your answer âś“
We can check our answer by applying the Distributive Property and comparing the result with the given expression.
After applying the Distributive Property and simplifying, the result is the same as the given expression. Therefore, we can be sure our solution is correct!
