Solve the Cubic Equation: x³-7x²+6x=0 Using Factoring

Cubic Factoring with GCF Method

x37x2+6x=0 x^3-7x^2+6x=0

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:05 Let's find the value of X.
00:08 First, factor out the term with X.
00:19 Next, take out the common factor from inside the parentheses.
00:34 Great job! This is one solution that makes the equation equal zero.
00:38 Now, let's check which solutions make the second term zero.
00:43 We'll factor using the trinomial. Let's identify the coefficients.
00:49 We need two numbers that add up to B, which is negative 7.
00:53 Plus, their product should equal C, which is positive 6.
00:58 Once we've found these numbers, we substitute them back in the parentheses.
01:02 Let's find the values that make each term zero.
01:07 And that's how we solve this problem. Well done!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

x37x2+6x=0 x^3-7x^2+6x=0

2

Step-by-step solution

To solve the given cubic equation x37x2+6x=0 x^3 - 7x^2 + 6x = 0 , follow these steps:

  • Step 1: Identify that the equation can be factored by its Greatest Common Factor (GCF).

There is an x x common in all terms: x(x27x+6)=0 x(x^2 - 7x + 6) = 0

  • Step 2: Factor the quadratic expression x27x+6 x^2 - 7x + 6 .

Look for two numbers that multiply to 6 6 (the constant term) and add up to 7 -7 (the coefficient of the linear term). The numbers are 1 -1 and 6 -6 . Thus:

x27x+6=(x1)(x6) x^2 - 7x + 6 = (x - 1)(x - 6)

  • Step 3: Set each factor equal to zero to solve for x x .

Now that the equation is fully factored as x(x1)(x6)=0 x(x - 1)(x - 6) = 0 , apply the zero product property:

x=0 x = 0 , x1=0 x - 1 = 0 (so x=1 x = 1 ), x6=0 x - 6 = 0 (so x=6 x = 6 )

Thus, the solutions to the equation x37x2+6x=0 x^3 - 7x^2 + 6x = 0 are x=0 x = 0 , x=1 x = 1 , and x=6 x = 6 .

3

Final Answer

x=0,1,6 x=0,1,6

Key Points to Remember

Essential concepts to master this topic
  • GCF Rule: Factor out the greatest common factor first
  • Technique: Find two numbers that multiply to 6 and add to -7: (-1)(-6)=6, -1+(-6)=-7
  • Check: Verify each solution: 0³-7(0)²+6(0)=0, 1³-7(1)²+6(1)=0, 6³-7(6)²+6(6)=0 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to factor out the GCF first
    Don't try to factor x³-7x²+6x directly without taking out the x = impossible to find factors! This wastes time and leads to confusion. Always factor out the greatest common factor x first, then work with the simpler quadratic x²-7x+6.

Practice Quiz

Test your knowledge with interactive questions

Break down the expression into basic terms:

\( 4x^2 + 6x \)

FAQ

Everything you need to know about this question

Why do I factor out x first instead of trying other methods?

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Every term has an x in it, making x the greatest common factor! Factoring it out first gives you x(x27x+6)=0 x(x^2-7x+6)=0 , which is much easier to work with than the original cubic.

How do I know which two numbers multiply to 6 and add to -7?

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List factor pairs of 6: (1,6) and (2,3). Since we need a sum of -7, try negative versions: (-1)+(-6)=-7 ✓. So the factors are (x1)(x6) (x-1)(x-6) .

Can a cubic equation really have exactly 3 solutions?

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Yes! A cubic equation can have up to 3 real solutions. In this case, we found all three: x=0, x=1, and x=6. Each factor gives us one solution using the zero product property.

What if I can't factor the quadratic part?

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If x27x+6 x^2-7x+6 didn't factor nicely, you could use the quadratic formula. But always try factoring first - it's usually faster when the numbers work out!

Why does x(x-1)(x-6)=0 give me three separate equations?

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This uses the zero product property: if a×b×c=0, then at least one of a, b, or c must equal zero. So we get three equations: x=0, x-1=0, and x-6=0.

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