Question

$\text{If}(a^3+b^3)=243\text{and}(a+b)=9,\text{then the value of}(a^2-ab+b^2)\text{is}$

• A. 9
• B. 27
• C. 18
• D. 36

Answer 1

The correct option is B 27

Using the identity
$(a^3+b^3)=(a+b)(a^2-ab+b^2)$,
$\Rightarrow 243=9(a^2-ab+b^2)$
$\Rightarrow (a^2-ab+b^2)=\frac{243}{9}=27$.