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Question

If $x + y + z = 0$, then the value of $\frac{x^2}{yz} + \frac{y^2}{zx} + \frac{z^2}{xy}$ is:

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
3

To solve the given problem, we need to find the value of the expression:

\(\frac{x^2}{yz} + \frac{y^2}{zx} + \frac{z^2}{xy}\)

given that \(x + y + z = 0\).

We can rewrite this condition as:

\(z = -(x + y)\)

Substituting \(z = -(x + y)\) into the expression gives us:

\(\frac{x^2}{y(-x-y)} + \frac{y^2}{x(-x-y)} + \frac{(-x-y)^2}{xy}\)

Simplifying each fraction:

\(\frac{x^2}{y(-x-y)} = -\frac{x^2}{y(x+y)}\)

\(\frac{y^2}{x(-x-y)} = -\frac{y^2}{x(x+y)}\)

\(\frac{(-x-y)^2}{xy} = \frac{x^2 + 2xy + y^2}{xy}\)

Thus, the expression can be rewritten as:

\(-\frac{x^2}{y(x+y)} - \frac{y^2}{x(x+y)} + \frac{x^2 + 2xy + y^2}{xy}\)

We can combine the first two terms:

\(-\left(\frac{x^3}{xy(x+y)} + \frac{y^3}{xy(x+y)}\right) = -\frac{x^3 + y^3}{xy(x+y)}\)

Using the identity \(x^3 + y^3 = (x+y)(x^2 - xy + y^2)\), and since \(z = -(x+y)\), we get:

\(x^3 + y^3 = -(x^2 - xy + y^2)(x+y)\)

So, the expression becomes:

\(\frac{x^2 + 2xy + y^2 - (x^2 - xy + y^2)}{xy} = 3\)

Hence, the final value of the expression is 3.

The correct option is 3.

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Similar Questions

  1. If $a + b + c = 10$ and $ab + bc + ca = 31$, find the value of $a^2 + b^2 + c^2$
  2. If $a + b + c = 0$, then find the value of $\frac{(a^2+b^2+c^2)^2}{a^2b^2+b^2c^2+c^2a^2}$

  3. If $x^4 + \frac{1}{x^4} = 322$, then $x^3 - \frac{1}{x^3} = ?$
  4. If $(x + \frac{1}{x}) = 7$, then $(x - \frac{1}{x})$ is equal to:
  5. What is the value of the following expression:

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  6. If $a + b + c = 17$, $abc = 168$, and $ab + bc + ca = 94$, then $a^3 + b^3 + c^3 = ?$
  7. If $a = \frac{b^2}{b - a}$, then the value of $a^3 + b^3$ is:
  8. If $ab = 10$ and $a^{2} + b^{2} = 29$, then $(a - b)^{2} = ?$
  9. Find the value of $\frac{(74 + 47)^2 + (74 - 47)^2}{74^2 + 47^2}$
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Important Questions from Identities

  1. If \(2x + { {1} \over 3x}= 5, x ≠ 0\) , then what is the value of  \(27x^3+{{1} \over 8x^3}\) ?

  2. If x 2 + 4y 2 = 40, xy = 6 and x > 2y then the value of x - 2y is:

  3. \(\dfrac{(0.73)^3+(0.31)^3}{(0.73)^2-0.73\times0.31+(0.31)^2}\)
  4. \(\dfrac{(5.17-2.19)^2-(5.17+2.19)^2}{11.3223}\)
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