# Thread: Write linear equation in functional natation

1. ## Write linear equation in functional natation

Hey guys,

could somebody please check if the following is right?

Task: Write the linear equation 4x -9y = -45 in functional notation, and determine the x-and y-intercepts. Show your work using functional notation.

My work:

4x -9y = -45 is
-9y = -4x -45 is
y = -4/-9 x +5 is

f(x) = -4/-9 x +5

The x-intercept is where y=0
0 = -4/-9 x +5
-5 = -4/-9 x
x = -11.25

The y-intercept is where x=0
f(0) = -4/-9 (0) +5
f(0) = 0 +5
f(0) = 5

Is my whole work right or is there any mistake? Thank you.

2. ## Re: Write linear equation in functional natation

Originally Posted by ford2008
Task: Write the linear equation 4x -9y = -45 in functional notation, and determine the x-and y-intercepts. Show your work using functional notation.
$f(x)=\frac{4}{9}x+5$.

3. ## Re: Write linear equation in functional natation

Originally Posted by ford2008
Hey guys,

could somebody please check if the following is right?

Task: Write the linear equation 4x -9y = -45 in functional notation, and determine the x-and y-intercepts. Show your work using functional notation.

My work:

4x -9y = -45 is
-9y = -4x -45 is
y = -4/-9 x +5 is
-4/-9= 4/9 but you seem to recognize that later so it is just awkwardly written, not an error.

f(x) = -4/-9 x +5

The x-intercept is where y=0
0 = -4/-9 x +5
-5 = -4/-9 x
x = -11.25

The y-intercept is where x=0
f(0) = -4/-9 (0) +5
f(0) = 0 +5
f(0) = 5

Is my whole work right or is there any mistake? Thank you.
Yes, those are correct.

I realize you were told to "Write the linear equation 4x -9y = -45 in functional notation" but, frankly, it would have been simpler to use the original form.
With 4x -9y = -45, setting y to 0 gives 4x= -45 so that x= -45/4= -11.25 is the x-intercept. Setting x= 0, -9y= -45 so that y= 5 is the y intercept.