For f(x) = x - 2 / x, find f(-4), find x when f(x) = 0

[Tess]

Can anyone help?

For f(x) = x - 2 / x,

a) find f(-4)
b) find x when f(x) = 0

I think I understand the second part:

b) 0 = x - 2 / x

So I will multiply this by x which will get me here:

0 = x - 2

I will add +2 to both sides and get x = 2. Is this correct?

Then I need help with the first part:

a) f(-4) = -4-2/x

I don't know where to go from here or even if this is correct. Please help.

Tessa

 

[jwpaine]

For your first function, USE BRACKETS!
do you mean \(\displaystyle \large f(x) = \frac{x-2}{x}\)
or do you mean \(\displaystyle \large f(x) = x - \frac{2}{x}\)

If you need to evaluate for f(-4), then substitute -4 into every x. in f(x) = ...



On the second one, find the zero of the function f(x) = 0 so, assuming that you mean
\(\displaystyle \large f(x) = \frac{x-2}{x}\) you would set the numerator equal to zero, and solve for x. (Because a numerator of 0 ---> 0/x = 0)
So, x = 2.

 

[Tess]

f(x)

I do mean f(x) =(x-2)/x

It says find f(-4)

So I go like this: f(-4)=(-4-2)/-4

which is f(-4)=(-6)/4

and then where should I go from here?

 

[jwpaine]

Don't forget your sign next to your -4 at the end

f(x) = (x-2)/x

f(-4) = (-4-2)/-4

f(-4) = (-6)/-4

(negative / negative = +)

f(-4) = (6/4) = 1.5

Done!