Solve the Polynomial Equation: x⁵ - 4x⁴ = 0

Polynomial Equations with Common Factor Extraction

Solve the following problem:

x54x4=0 x^5-4x^4=0

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:03 Factor with the X term to the fourth power
00:12 Take out the common factor from the parentheses
00:22 This is one solution that zeroes the equation
00:27 Now let's check which solutions zero the second factor
00:32 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 problem:

x54x4=0 x^5-4x^4=0

2

Step-by-step solution

Shown below is the given problem:

x54x4=0 x^5-4x^4=0

Note that on the left side we are able to factor the expression by using a common factor.

The largest common factor for the numbers and variables in this case is x4 x^4 since the fourth power is the lowest power in the equation and therefore is included both in the term with the fifth power and in the term with the fourth power. Any power higher than this is not included in the term with the fourth power, which is the lowest, and therefore this is the term with the highest power that can be factored out as a common factor from all terms in the expression. Proceed to factor the expression.

x54x4=0x4(x4)=0 x^5-4x^4=0 \\ \downarrow\\ x^4(x-4)=0

Let's continue to the left side of the equation that we obtained in the last step. There is a multiplication of algebraic expressions and on the right side the number 0. Therefore, due to the fact that the only way to obtain 0 from a multiplication is to multiply by 0, at least one of the expressions in the multiplication on the left side must equal zero,

meaning:

x4=0/4x=±0x=0 x^4=0 \hspace{8pt}\text{/}\sqrt[4]{\hspace{6pt}}\\ x=\pm0\\ \boxed{x=0} (In this case taking the even root of the right side of the equation will yield two possibilities - positive and negative, however since we're dealing with zero, we only obtain one solution)

Or:

x4=0x=4 x-4=0\\ \downarrow\\ \boxed{x=4}

Let's summarize the solution of the equation:

x54x4=0x4(x4)=0x4=0x=0x4=0x=4x=0,4 x^5-4x^4=0 \\ \downarrow\\ x^4(x-4)=0 \\ \downarrow\\ x^4=0 \rightarrow\boxed{ x=0}\\ x-4=0 \rightarrow \boxed{x=4}\\ \downarrow\\ \boxed{x=0,4}

Therefore the correct answer is answer C.

3

Final Answer

x=4,x=0 x=4,x=0

Key Points to Remember

Essential concepts to master this topic
  • Factoring Rule: Extract the highest common power from all terms
  • Technique: Factor out x4 x^4 from x54x4 x^5 - 4x^4 to get x4(x4)=0 x^4(x - 4) = 0
  • Check: Substitute x = 0: 054(04)=0 0^5 - 4(0^4) = 0 and x = 4: 454(44)=0 4^5 - 4(4^4) = 0

Common Mistakes

Avoid these frequent errors
  • Incorrectly identifying the common factor
    Don't factor out x5 x^5 or just x x = missing solutions or creating impossible equations! The common factor must be the lowest power that appears in all terms. Always identify x4 x^4 as the highest power that divides both x5 x^5 and x4 x^4 .

Practice Quiz

Test your knowledge with interactive questions

Solve the following equation:


\( 2x^2-8=x^2+4 \)

FAQ

Everything you need to know about this question

Why do I factor out x⁴ instead of just x?

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You want to factor out the highest possible power that appears in all terms. Since both terms have at least x4 x^4 , factoring out x4 x^4 simplifies the equation more than factoring out just x x .

How do I know when a product equals zero?

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Use the Zero Product Property: if A×B=0 A \times B = 0 , then either A=0 A = 0 or B=0 B = 0 (or both). This means x4=0 x^4 = 0 OR x4=0 x - 4 = 0 .

Why does x⁴ = 0 only give x = 0?

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Even though x4 x^4 is an even power, zero to any power is still zero. So x4=0 x^4 = 0 means x=0 x = 0 (it's a root with multiplicity 4).

What if I tried to solve this without factoring?

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Without factoring, you'd need advanced techniques like the rational root theorem or graphing. Factoring is much simpler when there's a common factor - always look for it first!

How can I check if x = 4 and x = 0 are both correct?

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Substitute each value back: For x = 0: 054(04)=00=0 0^5 - 4(0^4) = 0 - 0 = 0 ✓
For x = 4: 454(44)=10244(256)=10241024=0 4^5 - 4(4^4) = 1024 - 4(256) = 1024 - 1024 = 0 ✓

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