If $ x + \frac{1}{15x} = 3, $ then the value of $9x^3 +\frac{1}{375x^3}$ will be :

237.6

If $ x + \frac{1}{15x} = 3, $

then the value of $9x^3 +\frac{1}{375x^3}$ = ?

We know that,

If x + y  = n

then, $x^3 + y^3$ = n³ - 3 × n × xy

= then, $ x^3+\frac{1}{3375x}$ =3³ - 3 × 3 ÷ 15  = \(\frac{132}{5}\)

Multiply the above equation by 9 to get the desired equation,

$9x^3 +\frac{1}{375x^3}$ = \(\frac{132}{5}\) × 9 = \(\frac{1188}{5}\) = 237.6