Factor 3x² + 26x + 56

Here we will show you how to factor the quadratic function 3x² + 26x + 56 using the box method. In other words, we will show you how to factor 3x squared plus 26x plus 56 (3x^2 + 26x + 56) using the box method. It is a 5-step process:

Step 1: The standard form of a quadratic equation is ax² + bx + c. We start by labeling the different parts of our equation 3x² + 26x + 56, like this:

a = 3
b = 26
c = 56

Step 2: Next, we need to draw a box and divide it into four squares:

4	12x	56
x	3x²	14x
	3x	14

We put 3x² (a) in the bottom left square and 56 (c) in the top right square, like this:

4	12x	56
x	3x²	14x
	3x	14

Step 3: In order to fill in the other two squares, we need to do some math. We have to find two numbers that multiply together to give us the product of 3 times 56 (a × c), and add together to equal 26 (b).

More specifically, 3 times 56 is 168. Therefore, we need to find the two numbers that multiply to equal 168, and add to equal 26.

? × ? = 168
? + ? = 26

After looking at this problem, we can see that the two numbers that multiply together to equal 168, and add together to equal 26, are 12 and 14, as illustrated here:

12 × 14 = 168
12 + 14 = 26

Now, we can fill in the last two squares in our box with 12x and 14x. Place 12x in the upper left square, and place 14x in the lower right square.

4	12x	56
x	3x²	14x
	3x	14

Step 4: Next, we need to find four final numbers to finish factoring our equation. We can see that our box is a 2 x 2 table made up of rows and columns.

Our goal is to find the numbers that, when multiplied together, result in the products in each square. We can do this by finding the greatest common factor in each row.

Let’s look at the top row. We have the terms 12x and 56. The greatest common factor of 12x and 56 is 4. Therefore, we write 4 to the left of the top row. You can see it here in the color green:

4	12x	56
x	3x²	14x
	3x	14

Next, let’s look at the bottom row. We have the terms 3x² and 14x. The greatest common factor of 3x² and 14x is x. Therefore, we write x to the left of the bottom row. You can see it here in the color blue:

4	12x	56
x	3x²	14x
	3x	14

To find the values below the table, we first divide 3x² by x (labeled in blue). This gives us 3x.

3x² ÷ x = 3x

You can see this value colored in orange below:

4	12x	56
x	3x²	14x
	3x	14

Next, we divide 14x by x (labeled in blue). This gives us 14.

14x ÷ x = 14

You can see this value colored in purple below:

4	12x	56
x	3x²	14x
	3x	14

Step 5: Now we have all of the information we need to finish factoring the equation. The values outside of the box are used to factor 3x² + 26x + 56. You simply put the values on the left in one set of parentheses, and the values below in another set of parentheses, to get the answer:

(x + 4)(3x + 14)

That’s it! Now you know how to factor the equation 3x² + 26x + 56.

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