Question Details

If  x x2 - 4 x + 1 = 1 9 ,  then the value  x3 + 1 x3 .

Options

A

729

B

1256

C

1839

D

2158

Show Answer

Correct Answer :

Option D

2158

Solution :

` tags. - HTML / MathML constraint: Paragraphs separated with `

...

`, `
` for line breaks, MathML `` tags, raw unicode characters for math signs (`-`, `+`, `=`, etc.), line containing `...` block must be in its own `

...

` or have `
` before and after it. No `display="block"` in `` tags. No LaTeX. Let's carefully construct the MathML content to follow all constraints. MathML snippet for $x + \frac{1}{x} = 13$: ```xml x + 1 x = 13 ``` MathML snippet for $x^3 + \frac{1}{x^3} = 2158$: ```xml x3 + 1 x3 = 2158 ``` Let's build the complete output carefully. 2158

The correct option is 2158.


Step 1: Simplify the given algebraic equation.

We are given:

x x2 - 4 x + 1 = 1 9

Taking the reciprocal on both sides (since x ≠ 0):

x2 - 4 x + 1 x = 9

Dividing each term in the numerator by x:

x - 4 + 1 x = 9

Adding 4 to both sides gives:

x + 1 x = 13


Step 2: Calculate the required expression.

We use the algebraic identity for the cube of a binomial:

( x + 1 x ) 3 = x3 + 1 x3 + 3 ( x + 1 x )

Substituting x + 1 x = 13 into the identity:

133 = x3 + 1 x3 + 3 ( 13 )

2197 = x3 + 1 x3 + 39

Subtracting 39 from both sides:

x3 + 1 x3 = 2197 - 39 = 2158

Thus, the value of the expression is 2158.

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