a³-b³=513 এবং a-b=3, ab=?
Correct Answer: Option B
\[\begin{array}{l}
{a^3} - {b^3} = 513\\
= > {(a - b)^3} + 3ab(a - b) = 513\\
= > {3^3} + 3 \times ab \times 3 = 513\\
= > 27 + 9ab = 513\\
= > 9ab = 513 - 27\\
= > 9ab = 486\\
= > ab = \frac{{486}}{9} = 54
\end{array}\]
Download our app for free and access thousands of MCQ questions with detailed solutions