Solve for X: Calculating the Area of a Rectangle with (x-7)(x+7)

The area of the rectangle below is equal to (x7)(x+7) (x-7)(x+7) .

Calculate x.

555191919

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:03 We'll use the formula for calculating rectangle area (side times side)
00:10 We'll substitute appropriate values according to the given data and solve for the area
00:13 This is the rectangle's area
00:17 We'll substitute the rectangle's area in the equation and solve for X
00:28 We'll use the square of binomials formula to expand the brackets
00:47 Calculate 7 squared
00:56 Isolate X
01:09 Take the square root to find possible solutions for X
01:14 And this is the solution to the problem

Step-by-step written solution

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1

Understand the problem

The area of the rectangle below is equal to (x7)(x+7) (x-7)(x+7) .

Calculate x.

555191919

2

Step-by-step solution

To find x x , we'll begin by calculating the area of the rectangle using its dimensions:

  • Step 1: Calculate the area A A using the dimensions 5 and 19:
    A=5×19=95 A = 5 \times 19 = 95
  • Step 2: Set up the equation using the difference of squares:
    (x7)(x+7)=x249 (x-7)(x+7) = x^2 - 49
  • Step 3: Equate to the area calculated:
    x249=95 x^2 - 49 = 95
  • Step 4: Solve for x2 x^2 :
    x2=95+49=144 x^2 = 95 + 49 = 144
  • Step 5: Solve for x x by taking the square root:
    x=±144=±12 x = \pm \sqrt{144} = \pm 12

Therefore, the solutions for x x are x=±12 x = \pm 12 .

3

Final Answer

±12 \pm12

Practice Quiz

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\( (2+x)(2-x)=0 \)

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