# How do you find the important parts of the equation to graph the function f(x) = -4x?

Oct 14, 2015

Refer to the explanation.

#### Explanation:

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

Substitute $y$ for $f \left(x\right)$.

$y = - 4 x$ is in the slope-intercept form of a linear equation $y = m x + b$, where $m$ is the slope, and $b$ is the y-intercept.

For $y = - 4 x ,$ $m = - 4$, and $b = 0$.

To find points on the line, substitute values for $x$ and solve for $y$.

Determine the value of $y$ if $x = 0$.

$y = - 4 \left(0\right) = 0$

So the point in which $x = 0$ is $\left(0 , 0\right)$.

To find a second point, substitute another value for $x$.

$x = 1 ,$ $y = - 4$

So now we have two points, $\left(0 , 0\right)$ and $\left(1 , - 4\right)$, that we can plot and then draw a straight line through the two points.

Alternatively, you can use the slope of $- 4$ to determine other points. You could start at the origin $\left(0 , 0\right)$, and move $4$ places down the y-axis, then move to the right $1$ place to the point $\left(1 , - 4\right)$ Conversely, you could move $4$ places up the y-axis and $1$ place to the left to get the point (-1,4). You can plot those points and draw a straight line through them.

graph{y=-4x [-10, 10, -5, 5]}