Solve the Rational Equation: x(x²-9)/(x²+3x) = 0

Rational Equations with Factoring and Domain Restrictions

Solve the following:


x(x29)x2+3x=0 \frac{x(x^2-9)}{x^2+3x}=0

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:12 Convert from 9 to 3 squared
00:15 Take X out of parentheses
00:22 Reduce what's possible
00:33 Use the shortened multiplication formulas
00:50 Reduce what's possible
01:00 Isolate X
01:05 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:


x(x29)x2+3x=0 \frac{x(x^2-9)}{x^2+3x}=0

2

Step-by-step solution

To solve this problem, we need to find the values of x x that make the equation x(x29)x2+3x=0 \frac{x(x^2-9)}{x^2+3x}=0 true. The steps are as follows:

  • Step 1: Simplify the Numerator
    The numerator is x(x29) x(x^2 - 9) . Recognize x29 x^2 - 9 as a difference of squares, which can be factored to (x3)(x+3) (x-3)(x+3) . Thus, the numerator becomes x(x3)(x+3) x(x-3)(x+3) .

  • Step 2: Simplify the Denominator
    The denominator is x2+3x x^2 + 3x , which can be factored as x(x+3) x(x + 3) .

  • Step 3: Rewrite the Equation
    Now, the equation is rewritten as:
    x(x3)(x+3)x(x+3)=0 \frac{x(x-3)(x+3)}{x(x+3)} = 0

  • Step 4: Cancel Common Factors
    Assuming x0 x \neq 0 (since division by zero is undefined), cancel x x and (x+3) (x+3) :
    x31=0 \frac{x-3}{1} = 0

  • Step 5: Solve for x x
    The reduced equation x3=0 x - 3 = 0 gives the solution x=3 x = 3 .

  • Step 6: Check for Restrictions
    We previously canceled x x and x+3 x+3 , so x0 x \neq 0 and x3 x \neq -3 must be considered as part of the domain.

Therefore, the solution to the problem is x=3 x = 3 .

This corresponds to choice 2 in the given multiple-choice options.

3

Final Answer

3

Key Points to Remember

Essential concepts to master this topic
  • Rule: A fraction equals zero when numerator is zero and denominator isn't
  • Technique: Factor and cancel: x(x3)(x+3)x(x+3)=x31 \frac{x(x-3)(x+3)}{x(x+3)} = \frac{x-3}{1}
  • Check: Verify solution doesn't make original denominator zero: x ≠ 0, -3 ✓

Common Mistakes

Avoid these frequent errors
  • Including x = 0 and x = -3 as solutions
    Don't include values that make the denominator zero = invalid solutions! These create division by zero, making the original equation undefined. Always check that solutions don't violate domain restrictions from the denominator.

Practice Quiz

Test your knowledge with interactive questions

Solve:

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

FAQ

Everything you need to know about this question

Why can't x = 0 be a solution even though it makes the numerator zero?

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Because x = 0 also makes the denominator zero! When both numerator and denominator are zero, we get 00 \frac{0}{0} , which is undefined, not zero.

What about x = -3? The numerator becomes zero there too.

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Same problem! When x = -3, the denominator x2+3x=(3)2+3(3)=99=0 x^2 + 3x = (-3)^2 + 3(-3) = 9 - 9 = 0 . Division by zero means x = -3 is not in the domain.

How do I know which factors I can cancel?

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You can cancel common factors from numerator and denominator only when they don't equal zero. After canceling, remember those restrictions still apply to your final answer!

Is there a quick way to find domain restrictions?

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Yes! Set the original denominator equal to zero and solve. Those values are never solutions, even if they make the numerator zero too.

Why is the answer just x = 3 and not x = ±3?

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After factoring and canceling, we get x3=0 x - 3 = 0 , which gives only x = 3. The x = -3 was eliminated because it makes the original denominator zero.

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