Factor 45x² + 92x + 39

Here we will show you how to factor the quadratic function 45x² + 92x + 39 using the box method. In other words, we will show you how to factor 45x squared plus 92x plus 39 (45x^2 + 92x + 39) 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 45x² + 92x + 39, like this:

a = 45
b = 92
c = 39

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

3	27x	39
5x	45x²	65x
	9x	13

We put 45x² (a) in the bottom left square and 39 (c) in the top right square, like this:

3	27x	39
5x	45x²	65x
	9x	13

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 45 times 39 (a × c), and add together to equal 92 (b).

More specifically, 45 times 39 is 1755. Therefore, we need to find the two numbers that multiply to equal 1755, and add to equal 92.

? × ? = 1755
? + ? = 92

After looking at this problem, we can see that the two numbers that multiply together to equal 1755, and add together to equal 92, are 27 and 65, as illustrated here:

27 × 65 = 1755
27 + 65 = 92

Now, we can fill in the last two squares in our box with 27x and 65x. Place 27x in the upper left square, and place 65x in the lower right square.

3	27x	39
5x	45x²	65x
	9x	13

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 27x and 39. The greatest common factor of 27x and 39 is 3. Therefore, we write 3 to the left of the top row. You can see it here in the color green:

3	27x	39
5x	45x²	65x
	9x	13

Next, let’s look at the bottom row. We have the terms 45x² and 65x. The greatest common factor of 45x² and 65x is 5x. Therefore, we write 5x to the left of the bottom row. You can see it here in the color blue:

3	27x	39
5x	45x²	65x
	9x	13

To find the values below the table, we first divide 45x² by 5x (labeled in blue). This gives us 9x.

45x² ÷ 5x = 9x

You can see this value colored in orange below:

3	27x	39
5x	45x²	65x
	9x	13

Next, we divide 65x by 5x (labeled in blue). This gives us 13.

65x ÷ 5x = 13

You can see this value colored in purple below:

3	27x	39
5x	45x²	65x
	9x	13

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 45x² + 92x + 39. 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:

(5x + 3)(9x + 13)

That’s it! Now you know how to factor the equation 45x² + 92x + 39.

Factoring Quadratics
Go here if you want to learn how to factor another quadratic function.

Factor 45x² + 92x + 47
Here is the next quadratic function on our list that we have factored for you.