Question

for the following equation, evaluate $f(1)$. $f(x)=2x^{4}-5x$

Explanation:

Step1: Differentiate the function

Using the power - rule $\frac{d}{dx}(x^n)=nx^{n - 1}$, for $y = 2x^{4}-5x$, we have $f'(x)=2\times4x^{3}-5\times1 = 8x^{3}-5$.

Step2: Substitute $x = 1$

Substitute $x = 1$ into $f'(x)$. So $f'(1)=8\times1^{3}-5$.
$f'(1)=8 - 5=3$.

Answer:

$3$