(i) If x = 1 + √2, then show that: { x - 1/x }³ = 8
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x=1+
2
.
Now,
(x−
x
1
)
3
=(1+
2
−(
1+
2
1
))
3
=[1+
2
−(
2
+1
1
)×(
2
−1
2
−1
)]
3
=[1+
2
−(
2−1
2
−1
)]
3
=[1+
2
−(
2
−1)]
3
=(1+
2
−
2
+1)
3
=2
3
=8.
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