Question

If $f\left(x\right)=x^3-3$ and $g\left(x\right)=7x^5$, what is the approximate value of $f\left(g\right(3.9\left)\right)$?

• A. $389.23$
• B. $938.32$
• C. $4261.48$
• D. $11086.57$
• E. $14257.91$

Answer 1

Answer: (A)

$389.23$

$f\left(x\right)=x^3-3;g\left(x\right)=7x^5$

$f\left(g\right(3.9\left)\right)$

$g\left(3.9\right)=7(3.9{)}^5$

$g\left(3.9\right)=6315.69393$

$f\left(6315.69393\right)=389.23$

The correct option is 'A'