The product of two numbers is 40. If the sum of both number is 13 then what is their difference?

1 answer

Let the two numbers be \( x \) and \( y \). We have the following system of equations based on the information given:

  1. \( xy = 40 \) (the product of the two numbers)
  2. \( x + y = 13 \) (the sum of the two numbers)

We can express \( y \) in terms of \( x \) using the second equation:

\[ y = 13 - x \]

Now, we can substitute this expression for \( y \) into the first equation:

\[ x(13 - x) = 40 \]

Expanding this, we have:

\[ 13x - x^2 = 40 \]

Rearranging gives us a standard quadratic equation:

\[ x^2 - 13x + 40 = 0 \]

To solve for \( x \), we can use the quadratic formula \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \), where \( a = 1, b = -13, c = 40 \):

\[ x = \frac{-(-13) \pm \sqrt{(-13)^2 - 4 \cdot 1 \cdot 40}}{2 \cdot 1} \]

Calculating the discriminant:

\[ (-13)^2 - 4 \cdot 1 \cdot 40 = 169 - 160 = 9 \]

Now substituting back into the formula:

\[ x = \frac{13 \pm \sqrt{9}}{2} = \frac{13 \pm 3}{2} \]

This gives us two possible solutions for \( x \):

  1. \( x = \frac{16}{2} = 8 \)
  2. \( x = \frac{10}{2} = 5 \)

From the \( x \) values, we can find the corresponding \( y \) values:

  • If \( x = 8 \), then \( y = 13 - 8 = 5 \).
  • If \( x = 5 \), then \( y = 13 - 5 = 8 \).

In both cases, the two numbers are \( 8 \) and \( 5 \).

Now, we find their difference:

\[ |x - y| = |8 - 5| = 3 \]

Thus, the difference between the two numbers is \( \boxed{3} \).