How do you find the slope and intercept to graph y = 5x - 9?

2 Answers
Nov 10, 2015

Looking at the m and c values of the equation.

Explanation:

General Form of a Straight Line Equation
The general form of an equation for a straight line is y=mx+c In your case m=5 and c=-9

The Gradient or 'Slope'
m tells us the gradient or 'slope'. In your case this is 5, which means for every one coordinate you move along on the x axis, your line will move up 5 coordinates in the y axis.

The y Intercept
As for the y intercept, this is given by the value of c. In your case this is -9. Since we know that x=0 on the y axis then we know -9 is reffering to the y coordinate. This means the y intercept is at the coordinate (0,-9)

The x Intercept
If you want to figure out the x intercept as well then follow the method below.

On the x axis we know that y=0 we can put this into our equation and rearrange to find the value for x at this point.

0=5x-9
9 = 5x (Add 9 to both sides)
9/5 =x (Divide by 5 on both sides)

We know know x = 9/5 or x=1.8

So the x intercept is at the point (1.8,0)

This should be enough information to draw the graph!

Nov 10, 2015

See the explanation.

Explanation:

y=5x-9 is in slope-intercept form for a linear equation, y=mx+b, where m is the slope and b is the y-intercept.

By definition, 5 is the slope or (5/1), and the y-intercept is -9.

The y-intercept is the value of y when x=0.

y=5(0)-9=-9
The point is (0,-9)

The x-intercept is the value of x when y=0.

0=5x-9

Add 9 to both sides.

9=5x

Divide both sides by 5.

9/5=x

Switch sides.

x=9/5=1.8
The point is (9/5,0)

You can plot the x and y-intercepts and draw a straight line through the two points.

graph{y=5x-9 [-14.49, 17.53, -11.41, 4.61]}