Solve x⁷ - 5x⁶ = 0: Factoring High-Degree Polynomials

Polynomial Factoring with Common Factors

Solve the following problem:

x75x6=0 x^7-5x^6=0

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:08 Let's find the value of X.
00:11 First, factor the term with X raised to the sixth power.
00:16 Now, take out the common factor from the parentheses.
00:27 Great! We found one solution that makes the equation zero.
00:32 Next, let's check which solutions make the second factor zero.
00:39 And that's the solution to our question!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following problem:

x75x6=0 x^7-5x^6=0

2

Step-by-step solution

Shown below is the given problem:

x75x6=0 x^7-5x^6=0

Note that on the left side we are able factor the expression using a common factor. The largest common factor for the numbers and letters in this case is x6 x^6 given that the sixth power is the lowest power in the equation. Therefore is included both in the term with the seventh power and in the term with the sixth power. Any power higher than this is not included in the term with the sixth power, which is the lowest. Therefore this is the term with the highest power that can be factored out as a common factor from all terms in the expression, so we'll continue to factor the expression:

x75x6=0x6(x5)=0 x^7-5x^6=0 \\ \downarrow\\ x^6(x-5)=0

Proceed 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, since 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:

x6=0/6x=±0x=0 x^6=0 \hspace{8pt}\text{/}\sqrt[6]{\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 due to the fact that we're dealing with zero, we only obtain one solution)

or:

x5=0x=5 x-5=0\\ \downarrow\\ \boxed{x=5}

Let's summarize the solution of the equation:

x75x6=0x6(x5)=0x6=0x=0x5=0x=5x=0,5 x^7-5x^6=0 \\ \downarrow\\ x^6(x-5)=0 \\ \downarrow\\ x^6=0 \rightarrow\boxed{ x=0}\\ x-5=0 \rightarrow \boxed{x=5}\\ \downarrow\\ \boxed{x=0,5}

Therefore the correct answer is answer A.

3

Final Answer

x=0,5 x=0,5

Key Points to Remember

Essential concepts to master this topic
  • Factoring: Identify the highest common factor first before solving
  • Technique: Factor out x6 x^6 to get x6(x5)=0 x^6(x-5)=0
  • Check: Substitute x=0 and x=5 back: 075(06)=0 0^7-5(0^6)=0

Common Mistakes

Avoid these frequent errors
  • Trying to solve without factoring first
    Don't attempt to solve x75x6=0 x^7-5x^6=0 directly by moving terms around = impossible to isolate x! This leads to confusion and wrong methods like trying to take seventh roots. Always factor out the greatest common factor first to simplify the equation.

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 x6 x^6 and not x7 x^7 ?

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You factor out the lowest power that appears in all terms. Since we have x7 x^7 and x6 x^6 , the greatest common factor is x6 x^6 because it's the highest power that divides into both terms.

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). So x6(x5)=0 x^6(x-5) = 0 means x6=0 x^6 = 0 or x5=0 x-5 = 0 .

Why doesn't x6=0 x^6 = 0 give me multiple solutions?

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Even though taking the 6th root usually gives positive and negative answers, zero is special! The 6th root of 0 is just 0, since 06=0 0^6 = 0 . There's no negative zero.

Can I check my answers?

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Always verify! For x=0: 075(06)=00=0 0^7 - 5(0^6) = 0 - 0 = 0
For x=5: 575(56)=56(55)=56(0)=0 5^7 - 5(5^6) = 5^6(5-5) = 5^6(0) = 0

What if I have a higher degree polynomial?

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The same principle applies! Always look for common factors first, then use the Zero Product Property. Higher degree polynomials might factor into more pieces, giving you more solutions.

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