Expanding (x + 9)² to Standard Form
The expression (x + 9)² represents the square of the binomial (x + 9). To rewrite it in standard form, we need to expand it using the distributive property or the FOIL method.
Understanding the Process
1. Distribute: We can use the distributive property twice:
- (x + 9)² = (x + 9)(x + 9)
- = x(x + 9) + 9(x + 9)
2. Simplify: Now, distribute each term:
- = x² + 9x + 9x + 81
3. Combine Like Terms: Combine the terms with 'x':
- = x² + 18x + 81
Standard Form
The standard form of a quadratic expression is ax² + bx + c, where a, b, and c are constants.
Therefore, the standard form of (x + 9)² is x² + 18x + 81.
Key Points
- Squaring a binomial: When you square a binomial, you're essentially multiplying it by itself.
- Distributive property: This property allows us to multiply each term within a set of parentheses by the term outside.
- FOIL method: This acronym (First, Outer, Inner, Last) helps remember the order of multiplication when expanding two binomials.