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  1. If x = 1 + √2 + √3, then the value of (2x4 – 8x3 – 5x2 + 26x – 28) is
    1. 6 √6
    2. 0
    3. 3 √6
    4. 2 √6
Correct Option: A

Given in the question ,
x - 1 = √2 + √3
On squaring both sides ,
x 2 – 2x + 1 = 2 + 3 + 2√6
⇒ x 2 - 2x - 4 = 2 √6
On squaring again,
⇒ x4 + 4x2 + 16 – 4x3 – 8x2 + 16x = 24
⇒ x4 – 4x3 – 4x2 + 16x – 8 = 0
⇒ 2x4 – 8x3 – 8x2 + 32x – 16 = 0
⇒ 2x4 – 8x3 – 5x2 + 26x – 28 – 3x2 + 6x + 12 = 0
⇒ 2x4 – 8x3 – 5x2 + 26x – 28 = 3x2 – 6x – 12
⇒ 2x4 – 8x3 – 5x2 + 26x – 28 = 3 (x2 – 2x – 4)
⇒ 2x4 – 8x3 – 5x2 + 26x – 28 = 3 x 2√6 = 6 √6



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