Question

plz solve it write steps

Answer 1

${x}^{3} - {y}^{3} = (x - y)( {x}^{2} + {y}^{2} + xy)$
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...