Math Problem Statement

The length of a rectangle is (4x + 9) and the width is (5x - 7). What is the area of the rectangle?

Solution

To find the area of the rectangle, given its length and width, we use the formula for the area of a rectangle:

A=Length×WidthA = \text{Length} \times \text{Width}

Given:

  • Length, L=4x+9L = 4x + 9
  • Width, W=5x7W = 5x - 7

Step 1: Multiply LL and WW

A=(4x+9)(5x7)A = (4x + 9)(5x - 7)

Step 2: Use the distributive property (FOIL method) to expand this expression

A=(4x)(5x)+(4x)(7)+(9)(5x)+(9)(7)A = (4x)(5x) + (4x)(-7) + (9)(5x) + (9)(-7)

Step 3: Simplify each term

  1. (4x)(5x)=20x2(4x)(5x) = 20x^2
  2. (4x)(7)=28x(4x)(-7) = -28x
  3. (9)(5x)=45x(9)(5x) = 45x
  4. (9)(7)=63(9)(-7) = -63

Step 4: Combine like terms

A=20x2+(28x+45x)63A = 20x^2 + (-28x + 45x) - 63 A=20x2+17x63A = 20x^2 + 17x - 63

Final Answer:

The area of the rectangle is:

20x2+17x63\boxed{20x^2 + 17x - 63}

This corresponds to the option on the orange tile.

Would you like further details, or have any questions?

Here are five related questions:

  1. How do we determine which terms to combine in the expansion?
  2. What is the significance of using the distributive property in polynomial multiplication?
  3. How do we verify the final area expression through substitution?
  4. How would the result change if either the length or width expression was different?
  5. How do we interpret negative terms in the context of area?

Tip: When expanding binomials, carefully handle each term, especially with signs, to avoid calculation errors.

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Math Problem Analysis

Mathematical Concepts

Algebra
Polynomials
Area Calculation

Formulas

Area of a rectangle: A = Length × Width

Theorems

Distributive Property (FOIL method for binomials)

Suitable Grade Level

Grades 8-10