Question

if x + 1/7 is 7 then x³- 1/x is ​

Answer 1

Answer:

It is given that,

x+1/x=7..........(1)

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we know the algebraic identity,

a³+b³+3ab(a+b) =(a+b)³

or

a³+b³=(a+b)³-3ab(a+b)

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x³+1/x³=(x+1/x)³-3×x×1/x(x+1/x)

= (x+1/x³) -3(x+1/x)

= 7³-3×7

=7(7²-3)

=7(49-3)

=7×46

=322

I hope this helps you.