Question

question 1-4
selected response:1 point for correct answer only.
which of the following is not a root of the function below?
$f(x)=x^4 - 3x^2 - 4$

• $-2$
• $-1$
• $i$
• $2$

Explanation:

Step1: Substitute $x=-2$ into $f(x)$

$f(-2)=(-2)^4 - 3(-2)^2 - 4 = 16 - 12 - 4 = 0$

Step2: Substitute $x=-1$ into $f(x)$

$f(-1)=(-1)^4 - 3(-1)^2 - 4 = 1 - 3 - 4 = -6$

Step3: Substitute $x=i$ into $f(x)$

$f(i)=(i)^4 - 3(i)^2 - 4 = 1 - 3(-1) - 4 = 1 + 3 - 4 = 0$

Step4: Substitute $x=2$ into $f(x)$

$f(2)=(2)^4 - 3(2)^2 - 4 = 16 - 12 - 4 = 0$

Answer:

B. $-1$