If x^3 + 1/x^3 = 51 then value of x^3 - 1/x^3 is
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Answer:
a
3
−b
3
=(a−b)(a
2
+b
2
+ab)
So,
x
3
−
x
3
1
=(x−
x
1
)(x
2
+
x
2
1
+x×
x
1
)
=(x−
x
1
)(x
2
+
x
2
1
+1)
=(x−
x
1
)(51+1)
=52(x−
x
1
)
Now,
(x−
x
1
)
2
=x
2
+
x
2
1
−2x×
x
1
(x−
x
1
)
2
=51−2=49
x−
x
1
=
49
=7
Therefore,
x
3
−
x
3
1
=52(x−
x
1
)
=52×7
=364
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