Chapter 1: Problem 37
Solve the equation or inequality. Express the solutions in terms of intervals whenever possible. $$\frac{3 x+1}{5 x+7}=\frac{6 x+11}{10 x-3}$$
Short Answer
Expert verified
The solution is \(x = -\frac{5}{6}\).
Step by step solution
01
Cross Multiply
To eliminate the fractions, we cross-multiply. Set \\[ (3x + 1)(10x - 3) = (6x + 11)(5x + 7) \]This gives us two new algebraic expressions without denominators.
02
Expand Both Sides
Now we need to expand both sides of the equation:- Left side: \[ 3x \cdot 10x + 3x \cdot (-3) + 1 \cdot 10x + 1 \cdot (-3) = 30x^2 - 9x + 10x - 3 \] Simplify to get: \[ 30x^2 + x - 3 \]- Right side: \[ 6x \cdot 5x + 6x \cdot 7 + 11 \cdot 5x + 11 \cdot 7 = 30x^2 + 42x + 55x + 77 \] Simplify to get: \[ 30x^2 + 97x + 77 \]
03
Set Up the Equation
After expanding, set both sides equal and simplify:\[ 30x^2 + x - 3 = 30x^2 + 97x + 77 \]Subtract \(30x^2\) from both sides to further simplify: \\[ x - 3 = 97x + 77 \]
04
Solve for x
Rearrange the terms to isolate \(x\) on one side:\[ x - 97x = 77 + 3 \]Combine like terms:\[ -96x = 80 \]Divide both sides by \(-96\) to solve for \(x\):\[ x = \frac{80}{-96} = -\frac{5}{6} \]
05
Check for Extraneous Solutions
Verify that \(x = -\frac{5}{6}\) is not an extraneous solution by checking the original denominators:- For \(5x + 7\), substitute \(x = -\frac{5}{6}\): \[ 5\left(-\frac{5}{6}\right) + 7 = \frac{-25}{6} + \frac{42}{6} = \frac{17}{6} eq 0 \]- For \(10x - 3\), substitute \(x = -\frac{5}{6}\): \[ 10\left(-\frac{5}{6}\right) - 3 = \frac{-50}{6} - \frac{18}{6} = \frac{-68}{6} eq 0 \]Since neither denominator equals zero, \( x = -\frac{5}{6} \) is a valid solution.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cross-Multiplication
When solving rational equations, cross-multiplication is a powerful technique to eliminate fractions. It helps simplify the problem by creating a single variable equation.
- Begin by multiplying the numerator of the first fraction by the denominator of the second fraction.
- Then, multiply the numerator of the second fraction by the denominator of the first fraction.
- After cross-multiplying, equate the two resulting expressions to form a new equation.
Quadratic Expressions
Quadratic expressions often emerge when solving rational equations using cross-multiplication. Recognizing and simplifying these can simplify your path toward finding solutions.
- A quadratic expression usually takes the form \( ax^2 + bx + c \).
- These expressions can result from expanding products such as \((3x+1)(10x-3)\).
- After expanding, always combine like terms to simplify; for example, \(30x^2 - 9x + 10x - 3\) simplifies to \(30x^2 + x - 3\).
Extraneous Solutions
In mathematical equations, particularly rational ones, extraneous solutions can pop up unexpectedly. These are solutions that make the original equation undefined or don't satisfy it upon re-evaluation.
- After solving, always substitute back into the original equation to check validity.
- Pay special attention to variables in the denominators, as these could make expressions undefined if they turn zero.
- In our example, checking \( x = -\frac{5}{6} \) against original denominators \( 5x + 7 \) and \( 10x - 3 \), neither equaled zero, confirming it's a valid solution.
Interval Notation
Interval notation is a way of representing a set of solutions or possible values of a variable in mathematics. Although our particular problem resulted in just one solution, understanding and using interval notation is important.
- It expresses solution sets compactly, covering ranges of values.
- Closed intervals use square brackets \([a, b]\), indicating endpoints are included.
- Open intervals use parentheses \((a, b)\), meaning endpoints are not included.