For all numbers, x, the function f is defined by f(x) = ax^3/3, where

Question

For all numbers, x, the function f is defined by  f(x) = \frac{ax^3}{3} , where a is a constant. If f(3) = 45, then a =

A 3
B 5
C 15
D 30
E 35

Archit3110 · Answer

given 
 f(x) = \frac{ax^3}{3} 
f(3) = a * 3*3*3/ 3
45= a * 9
a = 5
IMO B

Kinshook · Answer

Given: For all numbers, x, the function f is defined by  f(x) = \frac{ax^3}{3} , where a is a constant. 
Asked: If f(3) = 45, then a =

f(3) = a3^3/3 = 9a = 45
a = 5

IMO B

BrushMyQuant · Answer

↧↧↧ Detailed Video Solution to the Problem ↧↧↧

https://www.youtube.com/watch?v=mAHtfOtaxzU

Given that  f(x) = \frac{ax^3}{3}  and f(3) = 45 and we need to find the value of a

To find –f(3) we need to compare what is inside ( ) in f(3) and f(x)

=> We need to substitute x with 3 in  f(x) = \frac{ax^3}{3}  to get the value of f(3)

=>  f(3) = \frac{a(3)^3}{3}  =  \frac{a*27}{3}  = 9a = 45 (given)

=> a =  \frac{45}{9}  = 5

So,  Answer will be B 
Hope it helps!

Watch the following video to MASTER Functions and Custom Characters

https://www.youtube.com/watch?v=b7JoMX0gk8M

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