Let's denote the two numbers as \( x \) and \( y \). According to the problem, we have the following equations:
- \( x + y = 100 \)
- \( xy = 900 \)
We can solve for one of the variables using the first equation. Let's solve for \( y \):
\[ y = 100 - x \]
Now, substitute \( y \) into the second equation:
\[ x(100 - x) = 900 \]
Expanding this gives:
\[ 100x - x^2 = 900 \]
Rearranging this into a standard quadratic form:
\[ x^2 - 100x + 900 = 0 \]
Now we can use the quadratic formula to solve for \( x \):
\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]
In this case, \( a = 1 \), \( b = -100 \), and \( c = 900 \):
\[ x = \frac{100 \pm \sqrt{(-100)^2 - 4 \cdot 1 \cdot 900}}{2 \cdot 1} \]
Calculating the discriminant:
\[ x = \frac{100 \pm \sqrt{10000 - 3600}}{2} \]
\[ x = \frac{100 \pm \sqrt{6400}}{2} \]
\[ x = \frac{100 \pm 80}{2} \]
Now, we have two possible solutions for \( x \):
- \( x = \frac{180}{2} = 90 \)
- \( x = \frac{20}{2} = 10 \)
Now we can find the corresponding values of \( y \):
- If \( x = 90 \), then \( y = 100 - 90 = 10 \).
- If \( x = 10 \), then \( y = 100 - 10 = 90 \).
Thus, the two numbers are \( 90 \) and \( 10 \).