
Here we will show you how to factor the quadratic function 81x² + 96x + 23 using the box method. In other words, we will show you how to factor 81x squared plus 96x plus 23 (81x^2 + 96x + 23) 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 81x² + 96x + 23, like this:
a = 81
b = 96
c = 23
Step 2: Next, we need to draw a box and divide it into four squares:
1 | 27x | 23 |
3x | 81x² | 69x |
27x | 23 |
1 | 27x | 23 |
3x | 81x² | 69x |
27x | 23 |
More specifically, 81 times 23 is 1863. Therefore, we need to find the two numbers that multiply to equal 1863, and add to equal 96.
? × ? = 1863
? + ? = 96
After looking at this problem, we can see that the two numbers that multiply together to equal 1863, and add together to equal 96, are 27 and 69, as illustrated here:
27 × 69 = 1863
27 + 69 = 96
Now, we can fill in the last two squares in our box with 27x and 69x. Place 27x in the upper left square, and place 69x in the lower right square.
1 | 27x | 23 |
3x | 81x² | 69x |
27x | 23 |
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 23. The greatest common factor of 27x and 23 is 1. Therefore, we write 1 to the left of the top row. You can see it here in the color green:
1 | 27x | 23 |
3x | 81x² | 69x |
27x | 23 |
1 | 27x | 23 |
3x | 81x² | 69x |
27x | 23 |
81x² ÷ 3x = 27x
You can see this value colored in orange below:
1 | 27x | 23 |
3x | 81x² | 69x |
27x | 23 |
Next, we divide 69x by 3x (labeled in blue). This gives us 23.
69x ÷ 3x = 23
You can see this value colored in purple below:
1 | 27x | 23 |
3x | 81x² | 69x |
27x | 23 |
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 81x² + 96x + 23. 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:
(3x + 1)(27x + 23)
That’s it! Now you know how to factor the equation 81x² + 96x + 23.
Factoring Quadratics
Go here if you want to learn how to factor another quadratic function.
Factor 81x² + 96x + 28
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