# If #f(x) = x^3 - 15/x#, what is #f(-1/3)#?

##### 1 Answer

Jan 29, 2016

#### Explanation:

To compute

#f(color(blue)(x)) = color(blue)(x)^3 - 15 / color(blue)(x)#

Replace each

#f(color(purple)(-1/3)) = (color(purple)(-1/3))^3 - 15 / (color(purple)(-1/3))#

#= - 1^3 / 3^3 + 15 / (1/3)#

... to resolve the double fraction, remember that dividing by

#= - 1 / 3^3 + 15 * 3#

#= - 1 / 27 + 45#

#= color(white)(x) 44 26/27 = 1214/27# ,

whichever formulation you prefer.

Hope that this helped!