# For F(x) = -4x how do you find f(-1)?

Feb 11, 2017

$f \left(- 1\right) = 4$

#### Explanation:

For the person who wrote this question, be very careful how you write your equation.

when you are writing your equation, ALWAYS use lower case.
If you put your function in upper case, as you did in the function, you are saying that the function in the anti-derivative. That is something that is in Calculus in high Math.
If you want to keep the function as a normal function, keep them in lower case as in $f \left(x\right) = - 4 x$ instead of $F \left(x\right) = - 4 x$

getting back to your function, when the question asks you to find f(-1), all it mentions is to put -1 in the function that was given.

$f \left(x\right) = - 4 x$
$f \left(- 1\right) = - 4 \left(- 1\right)$

The negatives will cancel out since a negative times a negative equals a positve

$f \left(- 1\right) = 4 \left(1\right)$
$f \left(- 1\right) = 4$

P.S.
Just in case if you are actually talking about the Calculus ways, I will also solve that for you. Forget about this if this is not what you are asking for and I am going way too advanced for you.

$F \left(x\right) = - 4 x$
$f \left(x\right) = \frac{- 4 {x}^{2}}{2}$
$f \left(x\right) = - 2 {x}^{2}$
$f \left(- 1\right) = - 2 {\left(- 1\right)}^{2}$
$f \left(- 1\right) = - 2 \left(1\right)$
$f \left(- 1\right) = - 2$