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Question

If $ab = 10$ and $a^{2} + b^{2} = 29$, then $(a - b)^{2} = ?$

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper PDF (31-Jan-2021) (Shift 1)
The correct answer is
9

Algebraic Identity Solution

We need to find the value of $(a - b)^{2}$ given the equations $ab = 10$ and $a^{2} + b^{2} = 29$.

Using the Algebraic Identity

Recall the algebraic identity for the square of a difference:

$ (a - b)^{2} = a^{2} - 2ab + b^{2} $

This can be rearranged as:

$ (a - b)^{2} = (a^{2} + b^{2}) - 2ab $

Substituting Given Values

We are given:

  • $a^{2} + b^{2} = 29$
  • $ab = 10$

Substitute these values into the identity:

$ (a - b)^{2} = (29) - 2(10) $

Calculating the Result

Perform the subtraction:

$ (a - b)^{2} = 29 - 20 $

$ (a - b)^{2} = 9 $

Therefore, the value of $(a - b)^{2}$ is 9.

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Similar Questions

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Important Questions from Identities

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

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