Factor 16x² + 70x + 76

Here we will show you how to factor the quadratic function 16x² + 70x + 76 using the box method. In other words, we will show you how to factor 16x squared plus 70x plus 76 (16x^2 + 70x + 76) 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 16x² + 70x + 76, like this:

a = 16
b = 70
c = 76

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

4	32x	76
2x	16x²	38x
	8x	19

We put 16x² (a) in the bottom left square and 76 (c) in the top right square, like this:

4	32x	76
2x	16x²	38x
	8x	19

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 16 times 76 (a × c), and add together to equal 70 (b).

More specifically, 16 times 76 is 1216. Therefore, we need to find the two numbers that multiply to equal 1216, and add to equal 70.

? × ? = 1216
? + ? = 70

After looking at this problem, we can see that the two numbers that multiply together to equal 1216, and add together to equal 70, are 32 and 38, as illustrated here:

32 × 38 = 1216
32 + 38 = 70

Now, we can fill in the last two squares in our box with 32x and 38x. Place 32x in the upper left square, and place 38x in the lower right square.

4	32x	76
2x	16x²	38x
	8x	19

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 32x and 76. The greatest common factor of 32x and 76 is 4. Therefore, we write 4 to the left of the top row. You can see it here in the color green:

4	32x	76
2x	16x²	38x
	8x	19

Next, let’s look at the bottom row. We have the terms 16x² and 38x. The greatest common factor of 16x² and 38x is 2x. Therefore, we write 2x to the left of the bottom row. You can see it here in the color blue:

4	32x	76
2x	16x²	38x
	8x	19

To find the values below the table, we first divide 16x² by 2x (labeled in blue). This gives us 8x.

16x² ÷ 2x = 8x

You can see this value colored in orange below:

4	32x	76
2x	16x²	38x
	8x	19

Next, we divide 38x by 2x (labeled in blue). This gives us 19.

38x ÷ 2x = 19

You can see this value colored in purple below:

4	32x	76
2x	16x²	38x
	8x	19

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 16x² + 70x + 76. 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:

(2x + 4)(8x + 19)

That’s it! Now you know how to factor the equation 16x² + 70x + 76.

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

Factor 16x² + 71x - 87
Here is the next quadratic function on our list that we have factored for you.