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Question

If $a + b + c = 10$ and $ab + bc + ca = 31$, find the value of $a^2 + b^2 + c^2$

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
38

Find $a^2 + b^2 + c^2$ Value

We are given the following information:

  • Sum of variables: $a + b + c = 10$
  • Sum of products of pairs: $ab + bc + ca = 31$

We need to find the value of $a^2 + b^2 + c^2$.

Algebraic Identity Application

We use the algebraic identity:

$ (a + b + c)^2 = a^2 + b^2 + c^2 + 2(ab + bc + ca) $

Substituting Given Values

Substitute the known values into the identity:

$ (10)^2 = a^2 + b^2 + c^2 + 2(31) $

Calculation Steps

Simplify the equation:

$ 100 = a^2 + b^2 + c^2 + 62 $

Isolate $a^2 + b^2 + c^2$:

$ a^2 + b^2 + c^2 = 100 - 62 $

$ a^2 + b^2 + c^2 = 38 $

Conclusion

The value of $a^2 + b^2 + c^2$ is 38.

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Similar Questions

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Important Questions from Identities

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

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