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The value of x+ y + z is 2 and xy + yz...

The value of `x+ y + z` is 2 and `xy + yz + zx ` is 11 , then find the value of `x^3 + y^3 + z^3 - 3xyz`.

A

72

B

76

C

74

D

-58

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the value of \( x^3 + y^3 + z^3 - 3xyz \) given that \( x + y + z = 2 \) and \( xy + yz + zx = 11 \). ### Step-by-step Solution: 1. **Identify the given values**: - \( x + y + z = 2 \) - \( xy + yz + zx = 11 \) 2. **Use the formula**: We will use the identity: \[ x^3 + y^3 + z^3 - 3xyz = (x + y + z) \left( (x + y + z)^2 - 3(xy + yz + zx) \right) \] 3. **Calculate \( (x + y + z)^2 \)**: \[ (x + y + z)^2 = 2^2 = 4 \] 4. **Substitute into the formula**: Now substitute \( x + y + z \) and \( xy + yz + zx \) into the formula: \[ x^3 + y^3 + z^3 - 3xyz = (2) \left( 4 - 3 \times 11 \right) \] 5. **Calculate \( 3 \times 11 \)**: \[ 3 \times 11 = 33 \] 6. **Substitute and simplify**: \[ x^3 + y^3 + z^3 - 3xyz = 2 \left( 4 - 33 \right) = 2 \left( -29 \right) \] 7. **Final calculation**: \[ 2 \times -29 = -58 \] Thus, the value of \( x^3 + y^3 + z^3 - 3xyz \) is \(-58\). ### Final Answer: \[ \boxed{-58} \]
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