Factor -92x² - 79x + 45

Here we will show you how to factor the quadratic function -92x² - 79x + 45 using the box method. In other words, we will show you how to factor negative 92x squared minus 79x plus 45 (-92x^2 - 79x + 45) 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 92x² + 79x - 45. Now we can label the different parts of our equation, like this:

a = 92
b = 79
c = -45

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

-9	-36x	-45
23x	92x²	115x
	4x	5

We put 92x² (a) in the bottom left square and -45 (c) in the top right square, like this:

-9	-36x	-45
23x	92x²	115x
	4x	5

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 92 times -45 (a × c), and add together to equal 79 (b).

More specifically, 92 times -45 is -4140. Therefore, we need to find the two numbers that multiply to equal -4140, and add to equal 79.

? × ? = -4140
? + ? = 79

After looking at this problem, we can see that the two numbers that multiply together to equal -4140, and add together to equal 79, are -36 and 115, as illustrated here:

-36 × 115 = -4140
-36 + 115 = 79

Now, we can fill in the last two squares in our box with -36x and 115x. Place -36x in the upper left square, and place 115x in the lower right square.

-9	-36x	-45
23x	92x²	115x
	4x	5

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 -36x and -45. The greatest common factor of -36x and -45 is -9. Therefore, we write -9 to the left of the top row. You can see it here in the color green:

-9	-36x	-45
23x	92x²	115x
	4x	5

Next, let’s look at the bottom row. We have the terms 92x² and 115x. The greatest common factor of 92x² and 115x is 23x. Therefore, we write 23x to the left of the bottom row. You can see it here in the color blue:

-9	-36x	-45
23x	92x²	115x
	4x	5

To find the values below the table, we first divide 92x² by 23x (labeled in blue). This gives us 4x.

92x² ÷ 23x = 4x

You can see this value colored in orange below:

-9	-36x	-45
23x	92x²	115x
	4x	5

Next, we divide 115x by 23x (labeled in blue). This gives us 5.

115x ÷ 23x = 5

You can see this value colored in purple below:

-9	-36x	-45
23x	92x²	115x
	4x	5

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 -92x² - 79x + 45. You simply put the values on the left in one set of parentheses, and the values below in another set of parentheses, to get:

(23x - 9)(4x + 5)

In our original quadratic equation, -92x² - 79x + 45, a is negative. Therefore, we need to add a negative (-) sign before our two sets of parentheses, like this:

-(23x - 9)(4x + 5)

That’s it! Now you know how to factor the equation -92x² - 79x + 45.

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