Common Factor Extraction Method: Identify the largest free number that we can extract. Then, let's move on to the variables and ask what is the least number of times the X appears in any element? Multiply the free number by the variable the same number of times we have found and we will obtain the greatest common factor.
To verify that you have correctly extracted the common factor, open theparentheses and see if you have returned to the original exercise.
Factoring out the greatest common factor is the first operation we try to carry out when we want to break down an expression into factors. We can remove from the parentheses a factor that is common to both elements and leave inside a simple and comfortable expression. The greatest common factor is the largest factor that is completely common to both elements.
Operation steps for extracting the common factor
Notice which is the largest free number we can extract. Then, let's move on to the unknowns and ask what is the least number of times that X appears in any element? Multiply the free number by the unknown the number of times we have found and we will obtain the greatest common factor. To verify that you have extracted the common factor correctly, open the parentheses and see if you have arrived at the original exercise.
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Let's look at an example of factoring out the common factor from the parentheses.
8x2+4x= Let's see what is the greatest common factor we can take out, the answer is 4. Now let's move on to the variable x. What is the minimum number of times that x appears in any term? The answer is 1. Now let's multiply the common factor obtained by the variable the number of times we have found and it will give us the greatest common factor. That is: 4×x=4x Let's take out4x as the common factor and we will obtain: 4x(2x+1) This is our factorization. When we want to find the solutions we will compare it with0 and it will give us: 4x(2x+1)=0 X=0 2x+1=0 2x=−1 x=−1/2 Therefore: x=0,−1/2
Don't worry, as you practice extracting the common factor you will not need to act according to the operation steps as we taught them, you will do the extraction of the common factor intuitively and quickly.
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Examples and exercises with solutions on factoring by taking out the common factor from the parentheses
Exercise #1
2x90−4x89=0
Video Solution
Step-by-Step Solution
The equation in the problem is:
2x90−4x89=0Let's pay attention to the left side:
The expression can be broken down into factors by taking out a common factor, The greatest common factor for the numbers and letters in this case is 2x89since the power of 89 is the lowest power in the equation and therefore included both in the term where the power is 90 and in the term where the power is 89.
Any power higher than that is not included in the term where the power of 89 is the lowest, and therefore it is the term with the highest power that can be taken out of all the terms in the expression as a common factor for the variables.
For the numbers, note that the number 4 is a multiple of the number 2, so the number 2 is the greatest common factor for the numbers for the two terms in the expression.
Continuing and performing the factorization:
2x90−4x89=0↓2x89(x−2)=0Let's continue and remember that on the left side of the equation that was obtained in the last step there is an algebraic expression and on the right side the number is 0.
Since the only way to get the result 0 from a product is for at leastone of the factors in the product on the left side to be equal to zero,
Meaning:
2x89=0/:2x89=0/89x=0
Or:
x−2=0x=2
In summary:
2x90−4x89=0↓2x89(x−2)=0↓2x89=0→x=0x−2=0→x=2↓x=0,2And therefore the correct answer is answer a.
Answer
x=0,2
Exercise #2
Solve the following by removing a common factor:
6x6−9x4=0
Video Solution
Step-by-Step Solution
First, we take out the smallest power
6x6−9x4=
6x4(x2−1.5)=0
If possible, we reduce the numbers by a common factor
Finally, we will compare the two sections with: 0
6x4=0
We divide by: 6x3
x=0
x2−1.5=0
x2=1.5
x=±23
Answer
x=0,x=±23
Exercise #3
Extract the common factor:
4x3+8x4=
Video Solution
Step-by-Step Solution
First, we use the power law to multiply terms with identical bases:
am⋅an=am+nIt is necessary to keep in mind that:
x4=x3⋅xNext, we return to the problem and extract the greatest common factor for the numbers separately and for the letters separately,
For the numbers, the greatest common factor is
4and for the letters it is:
x3and therefore for the extraction
4x3outside the parenthesis
We obtain the expression:
4x3+8x4=4x3(1+2x)To determine what the expression inside the parentheses is, we use the power law, our knowledge of the multiplication table, and the answer to the question: "How many times do we multiply the common factor that we took out of the parenthesis to obtain each of the terms of the original expression that we factored?
Therefore, the correct answer is: a.
It is always recommended to review again and check that you get each and every one of the terms of the expression that is factored when opening the parentheses (through the distributive property), this can be done in the margin, on a piece of scrap paper, or by marking the factor we removed and each and every one of the terms inside the parenthesis, etc.