Question

Mc Questions
1. Ifa-b=-8 and ab=-12, then
$a {3}^{} - b {3}{}$
is equal to​

Answer 1

Answer:

-224

Step-by-step explanation:

$a - b = - 8 \\ ab = -12 \\ \\ {(a - b)}^{2} = {( - 8)}^{2} \\ = > {a}^{2} + {b}^{2} - 2ab = 64 \\ = > {a}^{2} + {b}^{2} - 2 \times (-12) = 64 \\ = > {a}^{2} + {b}^{2} +24 = 64 \\ = > {a}^{2} + {b}^{2} = 40 \\ \\ { a}^{3} - { b}^{3} = (a - b)({a}^{2} +ab + {b}^{2} ) \\ = > { a}^{3} - { b}^{3} = ( - 8)(40 - 12) \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 28 \times ( - 8) \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = - 224$