Expanding (x + y - 7)²
The expression (x + y - 7)² represents the square of a trinomial. To expand this, we can use the FOIL method (First, Outer, Inner, Last) and the distributive property.
Step 1: Rewrite the expression
(x + y - 7)² = (x + y - 7)(x + y - 7)
Step 2: Apply the FOIL method
- First: x * x = x²
- Outer: x * y = xy
- Inner: x * -7 = -7x
- Last: y * y = y²
- Outer: y * -7 = -7y
- Inner: -7 * x = -7x
- Last: -7 * -7 = 49
Step 3: Combine like terms
x² + xy - 7x + y² - 7y - 7x + 49
Step 4: Simplify
x² + y² + 2xy - 14x - 14y + 49
Therefore, the expanded form of (x + y - 7)² is x² + y² + 2xy - 14x - 14y + 49.
Key Points:
- The FOIL method is a helpful tool for expanding products of binomials.
- Be careful when combining like terms, especially when dealing with multiple variables.
- Remember that squaring a trinomial involves multiplying it by itself.