Math Problem Statement

Solve the following rational equations. Note that your solutions will be graded based on the correctness of your LCD (1 point), correctness of the steps prior to the final answer (1 point), correctness of the solutions/roots (1 point) and correctness of the checking part (1 point). (16 points)

  1. r - 6 1 -------- = ------ 1- 4r r

Solution

Let's solve the rational equation step by step:

Given equation:

r614r=1r\frac{r - 6}{1 - 4r} = \frac{1}{r}

Step 1: Identify the Least Common Denominator (LCD)

To eliminate the denominators, we need to find the LCD of 14r1 - 4r and rr. The LCD is the product of these denominators:

LCD=r(14r)\text{LCD} = r(1 - 4r)

Step 2: Multiply both sides by the LCD

We multiply both sides of the equation by r(14r)r(1 - 4r) to eliminate the denominators:

r(14r)×r614r=r(14r)×1rr(1 - 4r) \times \frac{r - 6}{1 - 4r} = r(1 - 4r) \times \frac{1}{r}

On the left-hand side, the 14r1 - 4r cancels out, and on the right-hand side, the rr cancels out:

r(r6)=14rr(r - 6) = 1 - 4r

Step 3: Simplify the equation

Expand both sides:

r26r=14rr^2 - 6r = 1 - 4r

Step 4: Move all terms to one side of the equation

Let's bring all terms to one side to set the equation equal to zero:

r26r+4r1=0r^2 - 6r + 4r - 1 = 0

Simplify:

r22r1=0r^2 - 2r - 1 = 0

Step 5: Solve the quadratic equation

We can solve this quadratic equation using the quadratic formula:

r=(2)±(2)24(1)(1)2(1)r = \frac{-(-2) \pm \sqrt{(-2)^2 - 4(1)(-1)}}{2(1)}

Simplify the terms:

r=2±4+42r = \frac{2 \pm \sqrt{4 + 4}}{2}

r=2±82r = \frac{2 \pm \sqrt{8}}{2}

r=2±222r = \frac{2 \pm 2\sqrt{2}}{2}

r=1±2r = 1 \pm \sqrt{2}

So, the two possible solutions are:

r1=1+2,r2=12r_1 = 1 + \sqrt{2}, \quad r_2 = 1 - \sqrt{2}

Step 6: Check the solutions

We must check for any restrictions on rr. From the original equation, the denominator 14r1 - 4r and rr cannot be zero.

  1. r0r \neq 0 (from 1r\frac{1}{r}).
  2. 14r01 - 4r \neq 0 implies r14r \neq \frac{1}{4}.

Since neither 1+21 + \sqrt{2} nor 121 - \sqrt{2} violate these restrictions, both are valid solutions.

Final Answer:

The solutions to the equation are:

r=1+2,r=12r = 1 + \sqrt{2}, \quad r = 1 - \sqrt{2}


Would you like further details or clarifications?

Here are 5 related questions for practice:

  1. Solve x+32x5=4x\frac{x + 3}{2x - 5} = \frac{4}{x}.
  2. Solve 2yy+2=3y1\frac{2y}{y + 2} = \frac{3}{y - 1}.
  3. Solve 3a41a+2=5a22a8\frac{3}{a - 4} - \frac{1}{a + 2} = \frac{5}{a^2 - 2a - 8}.
  4. Find the LCD of 2xx3+3x+4\frac{2x}{x - 3} + \frac{3}{x + 4}.
  5. Solve b+6b24=3b2\frac{b + 6}{b^2 - 4} = \frac{3}{b - 2}.

Tip: Always check for excluded values that make denominators zero in rational equations!

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Math Problem Analysis

Mathematical Concepts

Algebra
Rational Equations
Quadratic Equations

Formulas

LCD (Least Common Denominator) concept
Quadratic equation formula: ax^2 + bx + c = 0
Quadratic formula: r = [-b ± sqrt(b^2 - 4ac)] / 2a

Theorems

Quadratic formula theorem
Rational equation properties

Suitable Grade Level

Grades 10-12