Expanding the Expression: (x-3)(x^2 + 3x + 9)
This expression represents the product of a binomial and a trinomial. We can expand it using the distributive property, also known as FOIL (First, Outer, Inner, Last).
Here's how to expand the expression:
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Multiply the first terms of each expression: x * x² = x³
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Multiply the outer terms: x * 3x = 3x²
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Multiply the inner terms: -3 * x² = -3x²
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Multiply the last terms: -3 * 9 = -27
Now, combine the terms:
x³ + 3x² - 3x² - 27
Simplifying the expression, we get:
x³ - 27
Therefore, the expanded form of (x-3)(x^2 + 3x + 9) is x³ - 27.
Understanding the pattern:
This expansion demonstrates a special pattern in algebra: the difference of cubes.
The expression (x³ - 27) can be factored as the difference of two cubes:
- x³ = (x)³
- 27 = (3)³
The general formula for the difference of cubes is:
a³ - b³ = (a - b)(a² + ab + b²)
In our example, a = x and b = 3.
Key takeaway:
Knowing how to expand and factor expressions like (x-3)(x^2 + 3x + 9) is essential for solving various algebraic problems and understanding mathematical patterns.