Verify the Equation: x⁴-16 = (x²-4)(4+x²) - Polynomial Identity Check

Polynomial Identities with Factorization Verification

Is the value of the following equation true or false?

x416=(x24)(4+x2) x^4-16=(x^2-4)(4+x^2)

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Is the equation correct?
00:15 We'll use the commutative law
00:27 We'll use the abbreviated multiplication formulas
00:47 Let's calculate 4 squared
00:52 The equation is correct
00:56 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Is the value of the following equation true or false?

x416=(x24)(4+x2) x^4-16=(x^2-4)(4+x^2)

2

Step-by-step solution

To solve this problem, let's follow these steps:

  • Step 1: Factor the left-hand side x416 x^4 - 16 using the difference of squares.
  • Step 2: Expand the right-hand side expression.
  • Step 3: Verify if both sides are equivalent after simplification.

Now, let's evaluate each step:

Step 1:
The expression on the left-hand side is x416 x^4 - 16 .
This can be viewed as (x2)242 (x^2)^2 - 4^2 ,
which is a difference of squares. Therefore, we can factor it as:
(x24)(x2+4)(x^2 - 4)(x^2 + 4).

Step 2:
Next, consider the right-hand side, (x24)(4+x2) (x^2 - 4)(4 + x^2) .
To expand, use distribution (FOIL method):
- First: x2×4=4x2 x^2 \times 4 = 4x^2
- Outer: x2×x2=x4 x^2 \times x^2 = x^4
- Inner: 4×4=16 -4 \times 4 = -16
- Last: 4×x2=4x2 -4 \times x^2 = -4x^2
Combine these terms:
x4+4x2164x2=x416 x^4 + 4x^2 - 16 - 4x^2 = x^4 - 16 .

Step 3:
The expanded term, x416 x^4 - 16 , matches the factored left-hand side expression, (x24)(x2+4) (x^2-4)(x^2+4) , showing that both sides are equivalent.

Therefore, the equation x416=(x24)(4+x2) x^4 - 16 = (x^2 - 4)(4 + x^2) is True for all values of x x .

3

Final Answer

True

Key Points to Remember

Essential concepts to master this topic
  • Identity Rule: Both sides must simplify to identical polynomial expressions
  • Technique: Factor left side: x416=(x2)242=(x24)(x2+4) x^4 - 16 = (x^2)^2 - 4^2 = (x^2-4)(x^2+4)
  • Check: Expand right side and verify it equals left side ✓

Common Mistakes

Avoid these frequent errors
  • Assuming order of factors matters in multiplication
    Don't think (x²-4)(4+x²) is different from (x²-4)(x²+4) = wrong conclusion! Order doesn't matter in multiplication due to the commutative property. Always recognize that (4+x²) = (x²+4) when verifying polynomial identities.

Practice Quiz

Test your knowledge with interactive questions

Solve:

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

FAQ

Everything you need to know about this question

Why can I factor x⁴ - 16 as a difference of squares?

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Because x4=(x2)2 x^4 = (x^2)^2 and 16=42 16 = 4^2 , so you have perfect squares being subtracted! This follows the pattern a2b2=(ab)(a+b) a^2 - b^2 = (a-b)(a+b) .

Does the order of terms in (4 + x²) vs (x² + 4) matter?

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No! Addition is commutative, so 4+x2=x2+4 4 + x^2 = x^2 + 4 . The expressions (x²-4)(4+x²) and (x²-4)(x²+4) are exactly the same.

How do I expand (x² - 4)(4 + x²) correctly?

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Use FOIL or distribution:

  • First: x2×4=4x2 x^2 \times 4 = 4x^2
  • Outer: x2×x2=x4 x^2 \times x^2 = x^4
  • Inner: 4×4=16 -4 \times 4 = -16
  • Last: 4×x2=4x2 -4 \times x^2 = -4x^2

Combined: x4+4x2164x2=x416 x^4 + 4x^2 - 16 - 4x^2 = x^4 - 16

Is this identity true for all values of x?

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Yes! Polynomial identities like this one are true for all real numbers. Unlike equations that have specific solutions, identities are always true regardless of what value you substitute for x.

What if I get confused about which side to factor?

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Start with the simpler-looking side first! In this case, x416 x^4 - 16 is easier to factor than expanding the right side. Once you factor it, compare with the given factored form.

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