If a + b = 10 and $\frac{3}{7}$ of ab = 9, then the value of $a^3 + b^3$ is :
Answer & explanation
Correct answer: option 3
If x + y = n
then, $x^3 + y^3$ = n3 - 3 × n × xy
If a + b = 10
$\frac{3}{7}$ of ab = 9,
so, by solving ab = 21
then the value of $a^3 + b^3$ = 103 - 3 × 10 × 21
= $a^3 + b^3$ = 1000 - 630 = 370