Question
Show that $: 13^3- 5^3$ is divisible by $8$
✓
Answer
$( 13^3- 5^3)$
[ Using identity $(a^3- b^3) = (a - b)(a^2+ab+ b^2)]$
$= ( 13 - 5 )( 13^2+ 13 \times 5 + 5^2)$
$= 8( 169 + 65 + 25 )$
Therefore$,$ the number is divisible by $ 8.$
[ Using identity $(a^3- b^3) = (a - b)(a^2+ab+ b^2)]$
$= ( 13 - 5 )( 13^2+ 13 \times 5 + 5^2)$
$= 8( 169 + 65 + 25 )$
Therefore$,$ the number is divisible by $ 8.$
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