Solve the Linear-Rational Equation: 11x - 1/x = 10

Rational Equations with Quadratic Solutions

Solve the following problem:

11x1x=10 11x-\frac{1}{x}=10

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:03 Multiply by the denominator to eliminate the fraction
00:14 Simplify what we can
00:18 Arrange the equation so one side equals 0
00:31 Convert -10 to -11 and add 1
00:38 Factor out the common term from the parentheses
00:45 Identify the common factor
00:49 Factor out this common term from the parentheses
00:56 Find what makes each factor equal zero
00:59 This is one solution
01:03 Use the same method and find what makes the second factor equal zero
01:10 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 problem:

11x1x=10 11x-\frac{1}{x}=10

2

Step-by-step solution

Let's solve the given equation:

11x1x=10 11x-\frac{1}{x}=10

Begin by eliminating the fraction line on the left side of the given equation. We can achieve this by multiplying both sides of the equation by the common denominator - which is the unknown x x . Note that the denominator (before multiplying by the common denominator - meaning in the given equation) cannot be zero since the fraction would be undefined. Therefore we must always define the domain accordingly, and the denominator should not be zero(mentioned in the first line of the solution below) This step is a mandatory step when solving an equation:

11x1x=10/xx0x11x11=x1011x21=10x11x210x1=0 11x-\frac{1}{x}=10 \hspace{8pt}\text{/}\cdot x\hspace{8pt}\Leftrightarrow \boxed{ x\neq0}\\ x\cdot 11x-1\cdot 1 =x\cdot10 \\ 11x^2-1=10x\\ 11x^2-10x-1=0\\ In the final stage after obtaining a quadratic equation where the coefficient of the first-degree term (of the unknown) is not zero (meaning such a term exists in the equation), we moved all terms to one side,

From here, we'll proceed to solve the expression using the quadratic formula.

Let's recall the quadratic formula:

The rule states that for a quadratic equation in the general form:

ax2+bx+c=0 ax^2+bx+c =0

there are two solutions (or fewer) which we find using the formula:

x1,2=b±b24ac2a x_{1,2}=\frac{-b\pm\sqrt{b^2-4ac}}{2a}

Let's return now to the equation that we obtained in the last stage:

11x210x1=0 11x^2-10x-1=0

Note the coefficients from the general form that we mentioned in the rule above:

ax2+bx+c ax^2+bx+c are:

{a=11b=10c=1 \begin{cases} a=11\\ b=-10\\ c=-1 \\ \end{cases}

We didn't forget to consider the coefficient together with its sign,

Therefore the solutions to the quadratic equation we obtained in the last stage are:

x1,2=(10)±(10)2411(1)211x1,2=10±100+4422x1,2=10±1222x1,2=2222,222x=1,111 x_{1,2}=\frac{-(-10)\pm\sqrt{(-10)^2-4\cdot11\cdot(-1)}}{2\cdot11}\\ x_{1,2}=\frac{10\pm\sqrt{100+44}}{22}\\ x_{1,2}=\frac{10\pm12}{22}\\ \downarrow\\ x_{1,2}=\frac{22}{22},\hspace{4pt}\frac{-2}{22}\\ \boxed{x=1,\hspace{4pt}-\frac{1}{11}}

In the final stage we simplified the fractions that were obtained as solutions,

Let's summarize then the solution of the equation:

11x1x=10/xx011x21=10x11x210x1=0x=1,111 11x-\frac{1}{x}=10 \hspace{8pt}\text{/}\cdot x\hspace{8pt}\Leftrightarrow \boxed{ x\neq0}\\ 11x^2-1=10x\\ 11x^2-10x-1=0\\ \boxed{x=1,\hspace{4pt}-\frac{1}{11}}

Note that both solutions we obtained for the unknown in the equation do not contradict the domain that was specified and therefore both are valid.

Therefore the correct answer is answer B.

3

Final Answer

x=1,x=111 x=1 , x=-\frac{1}{11}

Key Points to Remember

Essential concepts to master this topic
  • Domain Restriction: Identify where denominator equals zero before solving
  • Technique: Multiply by x: 11x² - 1 = 10x becomes quadratic
  • Check: Verify x ≠ 0 and substitute: 11(1) - 1/1 = 10 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting domain restrictions when clearing fractions
    Don't multiply by x without stating x ≠ 0 first = invalid solutions! The original equation is undefined when x = 0, so this must be excluded from possible solutions. Always identify domain restrictions before manipulating the equation.

Practice Quiz

Test your knowledge with interactive questions

Determine if the simplification shown below is correct:

\( \frac{7}{7\cdot8}=8 \)

FAQ

Everything you need to know about this question

Why do I need to state x ≠ 0 before solving?

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The original equation has 1x \frac{1}{x} which is undefined when x = 0. Even though we multiply by x to clear fractions, we must remember that x = 0 was never a valid solution to begin with.

How do I know this becomes a quadratic equation?

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When you multiply 11x1x=10 11x - \frac{1}{x} = 10 by x, you get 11x21=10x 11x^2 - 1 = 10x . Rearranging gives 11x210x1=0 11x^2 - 10x - 1 = 0 , which has as the highest power.

Can I use factoring instead of the quadratic formula?

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You can try! For 11x210x1=0 11x^2 - 10x - 1 = 0 , look for two numbers that multiply to (11)(-1) = -11 and add to -10. Since this doesn't factor easily, the quadratic formula is more reliable.

How do I check if my answers are correct?

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Substitute each solution back into the original equation:

  • For x = 1: 11(1)11=111=10 11(1) - \frac{1}{1} = 11 - 1 = 10
  • For x = -1/11: 11(111)1111=1+11=10 11(-\frac{1}{11}) - \frac{1}{-\frac{1}{11}} = -1 + 11 = 10

What if I got x = 0 as an answer?

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Reject it immediately! Since the original equation has 1x \frac{1}{x} , x = 0 would make the fraction undefined. This is why we state the domain restriction x ≠ 0 at the beginning.

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