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How to Find the Sum of Two Perfect Cubes

In mathematical terms, a "cube" refers to a value that is multiplied three times in a row. For instance, 2 times 2 times 2 equals 8. In this example, you would be cubing the number 2. The product 8 is a "perfect" cube because you can multiply 2 three times to reach this value. If you take a high school or college algebra or calculus course, you may have to find the sum of two perfect cubes. You can calculate this sum by following a basic formula.

Instructions

    • 1

      Write down the problem. For example, you might have y^3 + 125.

    • 2

      Calculate the cube root of both terms in the equation. The cube root is the value that is multiplied three times to reach the value in the equation. In this equation, the cube root of y^3 is y and the cube root of 125 is 5. Place these terms within a set of parentheses with a plus sign between the two terms -- (y + 5).

    • 3

      Square the first cube root and place it inside a second set of parentheses. In this example, the first cube root was y. If you square y, you multiply y times itself to get y^2. Therefore, the example would be (y + 5) (y^2....).

    • 4

      Multiply the two cube roots together to create the middle term in the second set of parentheses. Insert a plus sign to the left of this product. In this example, you would multiply y times 5 to get 5y. The solution would now look like (y + 5) (y^2 - 5y....).

    • 5

      Square the second cube root to create the final term in the second set of parentheses. A plus sign precedes this term. In this example, you would square 5 by multiplying 5 times 5 to get 25. Therefore, the completed solution would be (y + 5) (y^2 - 5y + 25).

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