Factor -38x² + 31x + 69

Here we will show you how to factor the quadratic function -38x² + 31x + 69 using the box method. In other words, we will show you how to factor negative 38x squared plus 31x plus 69 (-38x^2 + 31x + 69) using the box method. It is a 5-step process:

Step 1: The standard form of a quadratic equation is ax² + bx + c. In this equation, a is negative. Therefore, we need to start by setting aside the negative (-). We do this by flipping the signs in the equation to get 38x² - 31x - 69. Now we can label the different parts of our equation, like this:

a = 38
b = -31
c = -69

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

-69	-69x	-69
38x	38x²	38x
	x	1

We put 38x² (a) in the bottom left square and -69 (c) in the top right square, like this:

-69	-69x	-69
38x	38x²	38x
	x	1

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 38 times -69 (a × c), and add together to equal -31 (b).

More specifically, 38 times -69 is -2622. Therefore, we need to find the two numbers that multiply to equal -2622, and add to equal -31.

? × ? = -2622
? + ? = -31

After looking at this problem, we can see that the two numbers that multiply together to equal -2622, and add together to equal -31, are -69 and 38, as illustrated here:

-69 × 38 = -2622
-69 + 38 = -31

Now, we can fill in the last two squares in our box with -69x and 38x. Place -69x in the upper left square, and place 38x in the lower right square.

-69	-69x	-69
38x	38x²	38x
	x	1

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 -69x and -69. The greatest common factor of -69x and -69 is -69. Therefore, we write -69 to the left of the top row. You can see it here in the color green:

-69	-69x	-69
38x	38x²	38x
	x	1

Next, let’s look at the bottom row. We have the terms 38x² and 38x. The greatest common factor of 38x² and 38x is 38x. Therefore, we write 38x to the left of the bottom row. You can see it here in the color blue:

-69	-69x	-69
38x	38x²	38x
	x	1

To find the values below the table, we first divide 38x² by 38x (labeled in blue). This gives us x.

38x² ÷ 38x = x

You can see this value colored in orange below:

-69	-69x	-69
38x	38x²	38x
	x	1

Next, we divide 38x by 38x (labeled in blue). This gives us 1.

38x ÷ 38x = 1

You can see this value colored in purple below:

-69	-69x	-69
38x	38x²	38x
	x	1

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 -38x² + 31x + 69. You simply put the values on the left in one set of parentheses, and the values below in another set of parentheses, to get:

(38x - 69)(x + 1)

In our original quadratic equation, -38x² + 31x + 69, a is negative. Therefore, we need to add a negative (-) sign before our two sets of parentheses, like this:

-(38x - 69)(x + 1)

That’s it! Now you know how to factor the equation -38x² + 31x + 69.

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