Solve for X: Rational Equation 7/(6+3x-5(x+2)) = 1/(4(2-x))

Rational Equations with Cross-Multiplication Method

Solve for X:

76+3x5(x+2)=14(2x) \frac{7}{6+3x-5(x+2)}=\frac{1}{4(2-x)}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:04 Multiply by denominators to eliminate fractions
00:23 Carefully open parentheses properly, multiply by each factor
00:58 Collect like terms
01:06 Arrange the equation so that X is isolated on one side
01:22 Collect like terms
01:28 Isolate X
01:36 Factor 60 into 2 and 30
01:40 Factor 26 into 2 and 13
01:49 Simplify as much as possible
01:51 And this is the solution to the problem

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve for X:

76+3x5(x+2)=14(2x) \frac{7}{6+3x-5(x+2)}=\frac{1}{4(2-x)}

2

Step-by-step solution

To solve the given equation:

76+3x5(x+2)=14(2x) \frac{7}{6 + 3x - 5(x + 2)} = \frac{1}{4(2-x)}

we will follow these steps:

  • Simplify the expression inside the denominators.
  • Cross-multiply to eliminate the fractions.
  • Solve the resulting linear equation for xx.
  • Check the solution in the original equation to ensure there are no extraneous solutions.

Let's go through each step:

Step 1: Simplify the denominators
The first step is to simplify the expression in the denominator on the left-hand side: 6+3x5(x+2)6 + 3x - 5(x + 2).

Distribute the 5-5 in the expression:

6+3x5(x+2)    6+3x5x10 6 + 3x - 5(x + 2) \implies 6 + 3x - 5x - 10

Combine like terms:

610+3x5x    42x 6 - 10 + 3x - 5x \implies -4 - 2x

So, the equation becomes:

742x=14(2x) \frac{7}{-4 - 2x} = \frac{1}{4(2-x)}

Now, simplify 4(2x)4(2-x):

4(2x)=84x 4(2-x) = 8 - 4x

So the equation is:

742x=184x \frac{7}{-4 - 2x} = \frac{1}{8 - 4x}

Step 2: Cross-multiply to eliminate fractions
Cross-multiply to get rid of the fractions:

7×(84x)=1×(42x) 7 \times (8 - 4x) = 1 \times (-4 - 2x)

Distribute on both sides:

5628x=42x 56 - 28x = -4 - 2x

Step 3: Solve the linear equation for xx
Rearrange the equation to bring like terms together:

56+4=28x2x 56 + 4 = 28x - 2x

Simplify:

60=26x 60 = 26x

Divide both sides by 26 to solve for xx:

x=6026=3013 x = \frac{60}{26} = \frac{30}{13}

Step 4: Verify the solution
We need to ensure that our solution satisfies the original equation and doesn't create a situation where the denominator is zero:

We found x=3013x = \frac{30}{13}, so check that:

6+3x5(x+2)0 6 + 3x - 5(x + 2) \neq 0

Substitute x=3013x = \frac{30}{13} back into the simplified denominator:

42(3013)0 -4 - 2 \left(\frac{30}{13}\right) \neq 0

Calculate:

46013=526013=112130 -4 - \frac{60}{13} = \frac{-52 - 60}{13} = \frac{-112}{13} \neq 0

Thus, the solution is valid.

Therefore, the solution to the problem is x=3013 x = \frac{30}{13} .

3

Final Answer

3013 \frac{30}{13}

Key Points to Remember

Essential concepts to master this topic
  • Simplification: Distribute and combine like terms in complex denominators first
  • Cross-Multiply: 7(8-4x) = 1(-4-2x) becomes 56-28x = -4-2x
  • Verification: Check that x = 30/13 doesn't make any denominator zero ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to simplify denominators before cross-multiplying
    Don't leave 6+3x-5(x+2) unchanged = messy cross-multiplication with wrong results! Students often cross-multiply immediately without distributing -5(x+2) first, leading to calculation errors. Always simplify denominators completely before cross-multiplying.

Practice Quiz

Test your knowledge with interactive questions

Solve for X:

\( x - 3 + 5 = 8 - 2 \)

FAQ

Everything you need to know about this question

Why do I need to simplify the denominators first?

+

Simplifying denominators prevents calculation errors! In this problem, 6+3x5(x+2) 6+3x-5(x+2) becomes 42x -4-2x , making cross-multiplication much cleaner.

What happens if I get x = 2 as my answer?

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If x = 2, then 4(2x)=4(0)=0 4(2-x) = 4(0) = 0 , making the denominator zero! This means x = 2 is not allowed and would be an extraneous solution.

How do I know when to cross-multiply?

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Cross-multiply when you have one fraction equals another fraction. The pattern ab=cd \frac{a}{b} = \frac{c}{d} becomes ad = bc.

Can the answer be a fraction?

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Absolutely! x=3013 x = \frac{30}{13} is a perfectly valid answer. Many rational equations have fractional solutions. Just make sure to simplify and verify!

What if both denominators become zero with my answer?

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If your solution makes any denominator zero, it's not a valid solution. Always check each denominator separately with your final answer.

Do I need to factor the denominators?

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Not necessarily for cross-multiplication, but simplifying first (like we did with 6+3x5(x+2) 6+3x-5(x+2) ) makes the algebra much easier to handle.

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