Question

When the cube root of 8 is multiplied with the cube root of -8, the result obtained is _____.

• A. 8
• B. -8
• C. 4
• D. -4

Answer 1

The correct option is D -4

Prime factorisation of 8 is 2 x 2 x 2
So, cube root of 8:
$\sqrt[3]{38}=\sqrt[3]{32\times 2\times 2}$ = 2

Prime factorisation of -8 is -2 x -2 x -2
So, cube root of -8:
$\sqrt[3]{3-8}=\sqrt[3]{3-2\times -2\times -2}$ = -2

$\therefore \sqrt[3]{38}\times \sqrt[3]{3-8}=2\times -2=-4$