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Plz solve it write steps

Answer» {x}^{3} - {y}^{3} = (x - y)( {x}^{2} + {y}^{2} + xy)
We have to USE this formula.
{a}^{3} - {a}^{ - 3} = (a - {a}^{ - 1})( {a}^{2} + 1 + {a}^{ - 2} )
=>
a - {a}^{ - 1} \: is \: given \: a s \: 7.
=>
{a}^{3} - {a}^{ - 3} = 7( {a}^{2} + {a}^{ - 2} + 1)
since
{(a - {a}^{ - 1})}^{2} = {a}^{2} + {a}^{ - 2} - 1
50 = {a}^{2 } + {a}^{ - 2}
So a3-1/a3=7(50+1)=7(51)=357.
Thus 357 is the Answer. Hope it HELPS you...


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