Q7 of 26 Page 8

Find (x + 1)6 + (x – 1)6. Hence, or otherwise evaluate (√2 + 1)6 + (√2 – 1)6.

The Expression can be written as

(x + 1)6 + (x - 1)6 = 2[6C0x6 + 6C2x4 + 6C3x2 + 6C6x0]


= 2[x6 + 15x4 + 15x2 + 1]


Now, Putting x = √2 we get:


(√2 + 1)6 + (√2 – 1)6=


= 2[8 + 15 × 4 + 15 × 2 + 1]


= 2[8 + 60 + 30 + 1]


= 198


Hence, (√2 + 1)6 + (√2 – 1)6= 198


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