Math Problem Statement

The product of two numbers is 30. Their sum is 11. What are the two numbers?

Solution

We are given two pieces of information about two numbers:

  1. Their product is 30.
  2. Their sum is 11.

Let the two numbers be xx and yy. The information gives us the following system of equations:

xy=30(1)x \cdot y = 30 \quad \text{(1)} x+y=11(2)x + y = 11 \quad \text{(2)}

To solve for xx and yy, we can use substitution or the quadratic formula. Let's solve using substitution:

From equation (2), solve for yy:

y=11xy = 11 - x

Substitute this into equation (1):

x(11x)=30x \cdot (11 - x) = 30

Expand the equation:

x(11)x2=30x(11) - x^2 = 30 11xx2=3011x - x^2 = 30

Rearrange the equation:

x211x+30=0x^2 - 11x + 30 = 0

This is a quadratic equation. We can solve it using the quadratic formula:

x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

For the equation x211x+30=0x^2 - 11x + 30 = 0, the coefficients are a=1a = 1, b=11b = -11, and c=30c = 30. Substituting into the quadratic formula:

x=(11)±(11)24(1)(30)2(1)x = \frac{-(-11) \pm \sqrt{(-11)^2 - 4(1)(30)}}{2(1)} x=11±1211202x = \frac{11 \pm \sqrt{121 - 120}}{2} x=11±12x = \frac{11 \pm \sqrt{1}}{2} x=11±12x = \frac{11 \pm 1}{2}

So, the two possible values for xx are:

x=11+12=6orx=1112=5x = \frac{11 + 1}{2} = 6 \quad \text{or} \quad x = \frac{11 - 1}{2} = 5

If x=6x = 6, then from equation (2), y=116=5y = 11 - 6 = 5.

If x=5x = 5, then y=115=6y = 11 - 5 = 6.

Thus, the two numbers are 5 and 6.

Would you like a further explanation or details on solving quadratic equations?

Here are some related questions to consider:

  1. How do we derive the quadratic equation from a system of equations?
  2. What happens if the product and sum of the numbers were negative?
  3. Can we solve for more than two variables in a similar system of equations?
  4. How do you check the solutions to a quadratic equation?
  5. What is the significance of the discriminant in the quadratic formula?

Tip: When solving a quadratic equation, always check if the discriminant (the expression under the square root) is positive, zero, or negative. It helps you determine the number and type of solutions!

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Math Problem Analysis

Mathematical Concepts

Algebra
Systems of Equations
Quadratic Equations

Formulas

Quadratic equation formula ax^2 + bx + c = 0
Sum of two numbers: x + y = 11
Product of two numbers: x * y = 30

Theorems

Quadratic formula

Suitable Grade Level

Grades 7-9