Calculate Rectangle Area: Finding (x-7)(x+8) Using Algebraic Expressions

Question

What is the area of a rectangle with sides of x-7 and x+8?

Video Solution

Solution Steps

00:00 Calculate the rectangle's area
00:03 We'll use the formula for calculating a rectangle's area (side times side)
00:09 Let's properly expand the brackets, each term multiplies each term
00:29 Let's group terms and calculate the product
00:35 And this is the solution to the question

Step-by-Step Solution

To tackle this problem, we must compute the area of a rectangle given its sides are expressed as x7 x-7 and x+8 x+8 .

Step 1: Start by recognizing the formula used to calculate the area of a rectangle: the product of its length and width.

Step 2: Substitute the given expressions for length and width into this formula:

Area=(x7)(x+8) \text{Area} = (x-7)(x+8)

Step 3: Multiply the binomial expressions using the distributive property, often referred to as the FOIL method (First, Outer, Inner, Last).

  • First terms: x×x=x2 x \times x = x^2
  • Outer terms: x×8=8x x \times 8 = 8x
  • Inner terms: 7×x=7x -7 \times x = -7x
  • Last terms: 7×8=56 -7 \times 8 = -56

Step 4: Combine all these products into a single polynomial expression:

x2+8x7x56 x^2 + 8x - 7x - 56

Step 5: Simplify by combining like terms:

x2+(8x7x)56=x2+x56 x^2 + (8x - 7x) - 56 = x^2 + x - 56

Therefore, the area of the rectangle is given by the polynomial expression: x2+x56 x^2 + x - 56 .

Answer

x2+x56 x^2+x-56