How would you graph this 15x - 5y equals 30?

Answer 1

The first thing you need to do is get this equation to y=something, here's how you'd work that for this equation.

15x-5y=30

(subtract 15x from both sides)

5y=-15x+30

(now we're going to divide everything by 5 to get y by itself)

y=-3x+6

The graph of this equation is going to be a straight line with a slope of -3 and a y-intercept of 6

* * * * *

Here is a simpler way.

You do not have to rewrite the equation. Just leave it as it is: 15x - 5y = 30

Step 1A:

Cover up the y term so that the equation reads: 15x = 30

divide both sides by 15 so you get x = 2.

Step 1B:

Mark the point with coordinates x = 15, y = 0 ie (15, 0), and label it A.

Step 2A:

Cover up the x term so that the equation reads: -5y = 30

divide both sides by -5 so you get y = -6.

Step 2B:

Mark the point with coordinates x = 0, y = -6 ie (0, -6) and label it B.

Step 3:

Join AB and extend both ways.

Step 4:

Sit back and laugh at the people who rewrote the formula in the form y = something, got the slope and intercept, but don't know how that helps to graph the equation!