Solve Complex Equation: (x+8)(8-x) + 4(x-3)(x+3) + 5(6-x²) = 0

Quadratic Equations with Complex Factorization

Solve the following equation:

(x+8)(8x)+4(x3)(x+3)+5(6x2)=0 (x+8)(8-x)+4(x-3)(x+3)+5(6-x^2)=0

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 Use the commutative law
00:26 Use the shortened multiplication formulas
00:56 Calculate 8 squared
01:00 Expand the parentheses
01:30 Calculate the multiplications
01:36 Collect like terms
01:57 Isolate X
02:05 Break down 29 into square root of 29 squared
02:11 Again use the shortened multiplication formulas
02:20 Find the two possible solutions
02:39 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

Solve the following equation:

(x+8)(8x)+4(x3)(x+3)+5(6x2)=0 (x+8)(8-x)+4(x-3)(x+3)+5(6-x^2)=0

2

Step-by-step solution

To solve the equation (x+8)(8x)+4(x3)(x+3)+5(6x2)=0 (x+8)(8-x)+4(x-3)(x+3)+5(6-x^2)=0 , we will follow these steps:

  • Step 1: Expand and simplify each factor using important algebraic formulas.
  • Step 2: Combine all terms to form a quadratic equation.
  • Step 3: Solve the quadratic equation using the quadratic formula.

Let's work through each step:

Step 1: Expand each part of the equation:

  • The first term (x+8)(8x) (x+8)(8-x) is a difference of squares, which simplifies to:
    (x+8)(8x)=(82x2)=64x2 (x+8)(8-x) = (8^2 - x^2) = 64 - x^2 .
  • The second term 4(x3)(x+3) 4(x-3)(x+3) is another difference of squares:
    4[(x29)]=4x236 4[(x^2 - 9)] = 4x^2 - 36 .
  • The third term 5(6x2) 5(6-x^2) simplifies to:
    305x2 30 - 5x^2 .

Step 2: Combine the results to form a quadratic equation:

Combine terms in the equation:

64x2+4x236+305x2=0 64 - x^2 + 4x^2 - 36 + 30 - 5x^2 = 0

Simplify further:

(4x2x25x2)+(6436+30)=0 (4x^2 - x^2 - 5x^2) + (64 - 36 + 30) = 0

2x2+58=0 -2x^2 + 58 = 0

Rearrange to standard quadratic form:

2x2=58 2x^2 = 58

Step 3: Solve using the quadratic formula:

The equation simplifies to x2=29 x^2 = 29 .

Taking the square root of both sides gives the solutions:

x=±29 x = \pm \sqrt{29} .

Thus, the solution to the equation is ±29 \pm \sqrt{29} .

3

Final Answer

±29 ±\sqrt{29}

Key Points to Remember

Essential concepts to master this topic
  • Expansion: Use difference of squares formula (a+b)(a-b) = a² - b²
  • Technique: Combine like terms: -x² + 4x² - 5x² = -2x²
  • Check: Substitute x=29 x = \sqrt{29} back into original equation = 0 ✓

Common Mistakes

Avoid these frequent errors
  • Incorrectly expanding (x+8)(8-x)
    Don't expand as x² + 64 = wrong signs and missing terms! This ignores the negative sign and gives 2x² = -6 instead of -2x² = -58. Always recognize (a+b)(c-a) patterns and apply difference of squares correctly.

Practice Quiz

Test your knowledge with interactive questions

Solve:

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

FAQ

Everything you need to know about this question

Why is (x+8)(8-x) a difference of squares?

+

Rewrite it as (8+x)(8x) (8+x)(8-x) to see the pattern (a+b)(a-b). This equals 82x2=64x2 8^2 - x^2 = 64 - x^2 , which is much faster than FOIL!

How do I combine all those x² terms correctly?

+

Identify the coefficients: x2 -x^2 (coefficient -1), +4x2 +4x^2 (coefficient +4), and 5x2 -5x^2 (coefficient -5). Add them: -1 + 4 - 5 = -2, giving 2x2 -2x^2 .

Why don't we need the quadratic formula here?

+

After simplification, we got 2x2+58=0 -2x^2 + 58 = 0 , which rearranges to x2=29 x^2 = 29 . This is a pure quadratic (no x term), so we just take square roots!

What does ± mean in the answer?

+

The ± symbol means "plus or minus." When we solve x2=29 x^2 = 29 , we get two solutions: x=+29 x = +\sqrt{29} and x=29 x = -\sqrt{29} .

Can I simplify √29 further?

+

No, because 29 is a prime number with no perfect square factors other than 1. So 29 \sqrt{29} is already in simplest radical form.

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