Chapter 7: Problem 33
Solve the given quadratic equations by factoring. $$(x+2)^{3}=x^{3}+8$$
Short Answer
Expert verified
The solutions are \(x = 0\) and \(x = -2\).
Step by step solution
01
Recognize the Equation Form
The given equation \((x+2)^3 = x^3 + 8\) is in the form of a difference of cubes with \((a+b)^3 = a^3 + 3a^2b + 3ab^2 + b^3\). Notice that the original equation simplifies to this identity because \((x+2)^3 = x^3 + 6x^2 + 12x + 8\).
02
Rewrite the Equation
Convert the equation into a standard polynomial form by expanding the left side: \((x+2)^3 = (x+2)(x+2)(x+2) = x^3 + 6x^2 + 12x + 8\). Therefore, our equation is \(x^3 + 6x^2 + 12x + 8 = x^3 + 8\).
03
Simplify the Equation
Bring all terms to one side to simplify: \(x^3 + 6x^2 + 12x + 8 - x^3 - 8 = 0\). This simplifies to \(6x^2 + 12x = 0\).
04
Factor the Polynomial
Factor out the greatest common factor from each term: \(6x(x+2) = 0\). The two factors are \(6x = 0\) and \(x+2 = 0\).
05
Solve Each Factor for Zero
Set each factor equal to zero: For \(6x = 0\), divide by 6 to get \(x = 0\). For \(x+2 = 0\), subtract 2 from both sides to get \(x = -2\).
06
Verify the Solutions
Substitute \(x = 0\) and \(x = -2\) back into the original equation to verify. For \(x = 0\), the equation becomes \((2)^3 = 0^3 + 8\), which is true. For \(x = -2\), the equation becomes \(0 = 0+8\), which is also true.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Difference of Cubes
The 'Difference of Cubes' is a formula used when you come across expressions that look like two cubes being subtracted. Recognizing this pattern simplifies complex equations. The general formula is:
\[ a^3 - b^3 = (a-b)(a^2 + ab + b^2) \]
In our exercise, the equation \((x+2)^3 = x^3 + 8\) can be related to cube identities. Essentially, you recognize that the equation simplifies by expanding the cube on the left side:
\[ a^3 - b^3 = (a-b)(a^2 + ab + b^2) \]
In our exercise, the equation \((x+2)^3 = x^3 + 8\) can be related to cube identities. Essentially, you recognize that the equation simplifies by expanding the cube on the left side:
- When expanded, \((x+2)^3 = x^3 + 6x^2 + 12x + 8\), which does not directly appear as a difference of cubes.
Polynomial Factoring
Factoring polynomials involves breaking down a polynomial into simpler components, typically expressed as products of polynomials. In the simplified equation \(6x^2 + 12x = 0\), factoring comes into play for simplification.
Here's how you can efficiently factor a polynomial:
Here's how you can efficiently factor a polynomial:
- Identify the greatest common factor (GCF) of all the terms. In our case, the GCF is \(6x\).
- Factor out the GCF from each term to simplify the equation. So, \(6x^2 + 12x\) factors into \(6x(x+2) = 0\).
Quadratic Solutions
The final step of our exercise is solving the quadratic equation after it has been factored. We look at each factor from the factored polynomial equation \(6x(x+2) = 0\), solving them individually:
Solving quadratic equations through factoring provides a clear path from complex algebra to simple solutions. Once factors are found, each factor equates to zero, and from which straightforward algebraic solutions arise. This process transforms a seemingly daunting equation into a series of more accessible arithmetic steps.
- For \(6x = 0\): divide by 6 to obtain \(x = 0\).
- For \(x+2 = 0\): subtract 2 from both sides to solve for \(x = -2\).
Solving quadratic equations through factoring provides a clear path from complex algebra to simple solutions. Once factors are found, each factor equates to zero, and from which straightforward algebraic solutions arise. This process transforms a seemingly daunting equation into a series of more accessible arithmetic steps.