Find the value of 4x² + y² + 25z² + 4xy - 10yz - 20zx when x = 4, y = 3 and z = 2.
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Correct answer: A
Explanation
Given:
x = 4, y = 3, z = 2
4x² + y² + 25z² + 4xy − 10yz − 20zx
According to the formula:
4x² = 4 × 4² = 4 × 16 = 64
y² = 3² = 9
25z² = 25 × 2² = 25 × 4 = 100
4xy = 4 × 4 × 3 = 48
−10yz = −10 × 3 × 2 = −60
−20zx = −20 × 2 × 4 = −160
64 + 9 + 100 + 48 − 60 − 160 = 1