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Question

$p$ and $q$ are positive integers and $\frac{p}{q} + \frac{q}{p} = 3$,
then, $\frac{p^2}{q^2} + \frac{q^2}{p^2} = $

The correct answer is
7

Algebraic Solution for Fraction Equation

We are given that $p$ and $q$ are positive integers and the equation:

$ \frac{p}{q} + \frac{q}{p} = 3 $

We need to find the value of:

$ \frac{p^2}{q^2} + \frac{q^2}{p^2} $

Step-by-Step Calculation

  1. Let $x = \frac{p}{q}$. The given equation can be rewritten in terms of $x$ as:

    $ x + \frac{1}{x} = 3 $

  2. The expression we need to find is $\frac{p^2}{q^2} + \frac{q^2}{p^2}$, which is equivalent to $x^2 + \frac{1}{x^2}$.

  3. Consider the square of the term $(x + \frac{1}{x})$:

    $ \left(x + \frac{1}{x}\right)^2 = x^2 + 2(x)\left(\frac{1}{x}\right) + \left(\frac{1}{x}\right)^2 $

    $ \left(x + \frac{1}{x}\right)^2 = x^2 + 2 + \frac{1}{x^2} $

  4. Rearrange the formula to solve for $x^2 + \frac{1}{x^2}$:

    $ x^2 + \frac{1}{x^2} = \left(x + \frac{1}{x}\right)^2 - 2 $

  5. Substitute the given value $\left(x + \frac{1}{x} = 3\right)$ into the rearranged formula:

    $ x^2 + \frac{1}{x^2} = (3)^2 - 2 $

    $ x^2 + \frac{1}{x^2} = 9 - 2 $

    $ x^2 + \frac{1}{x^2} = 7 $

  6. Since $x = \frac{p}{q}$, we have $x^2 = \frac{p^2}{q^2}$ and $\frac{1}{x^2} = \frac{q^2}{p^2}$. Therefore:

    $ \frac{p^2}{q^2} + \frac{q^2}{p^2} = 7 $

Conclusion

The value of $\frac{p^2}{q^2} + \frac{q^2}{p^2}$ is 7.

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Important Questions from Algebra

  1. For positive non-zero real variables $x$ and $y$, if
    $ln\left(\frac{x+y}{2}\right) = \frac{1}{2} [ln\left(x\right) + ln\left(y\right)]$
    then, the value of $\frac{x}{y} + \frac{y}{x}$ is
  2. Given $f(x, y) = x^2 - 2xy + y^2$ 

    The complete contour of the equation $f(x, y) = 1$ is described by the option(s) ___.

  3. It is given that $x$ and $y$ are integers in the following equation:
    $$(x + y - 7)^2 + (y + 3x - 13)^2 = 0$$
    The value of $(x^3 + y^3)$ is ________ (in integer).
  4. If $pqr \neq 0$ and $p^{-x} = \frac{1}{q}$, $q^{-y} = \frac{1}{r}$, $r^{-z} = \frac{1}{p}$, what is the value of the product $xyz$?
  5. Two points $(4, p)$ and $(0, q)$ lie on a straight line having a slope of $3/4$. The value of $(p – q)$ is
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