
Here we will show you how to factor the quadratic function 25x² + 71x + 46 using the box method. In other words, we will show you how to factor 25x squared plus 71x plus 46 (25x^2 + 71x + 46) 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 25x² + 71x + 46, like this:
a = 25
b = 71
c = 46
Step 2: Next, we need to draw a box and divide it into four squares:
1 | 25x | 46 |
x | 25x² | 46x |
25x | 46 |
1 | 25x | 46 |
x | 25x² | 46x |
25x | 46 |
More specifically, 25 times 46 is 1150. Therefore, we need to find the two numbers that multiply to equal 1150, and add to equal 71.
? × ? = 1150
? + ? = 71
After looking at this problem, we can see that the two numbers that multiply together to equal 1150, and add together to equal 71, are 25 and 46, as illustrated here:
25 × 46 = 1150
25 + 46 = 71
Now, we can fill in the last two squares in our box with 25x and 46x. Place 25x in the upper left square, and place 46x in the lower right square.
1 | 25x | 46 |
x | 25x² | 46x |
25x | 46 |
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 25x and 46. The greatest common factor of 25x and 46 is 1. Therefore, we write 1 to the left of the top row. You can see it here in the color green:
1 | 25x | 46 |
x | 25x² | 46x |
25x | 46 |
1 | 25x | 46 |
x | 25x² | 46x |
25x | 46 |
25x² ÷ x = 25x
You can see this value colored in orange below:
1 | 25x | 46 |
x | 25x² | 46x |
25x | 46 |
Next, we divide 46x by x (labeled in blue). This gives us 46.
46x ÷ x = 46
You can see this value colored in purple below:
1 | 25x | 46 |
x | 25x² | 46x |
25x | 46 |
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 25x² + 71x + 46. 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:
(x + 1)(25x + 46)
That’s it! Now you know how to factor the equation 25x² + 71x + 46.
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