How do you graph the equation by plotting points 3x + 5y = 12?

2 Answers
Jun 7, 2016

First get the equation into standard form:
y= -3/5x + 12/5

Then, start plugging in values for x and plotting points.

Explanation:

Getting the equation to standard form

It will be much easier to plug in values if the equation is in standard form (so that y is isolated). First, subtract 3x from each side. This gives you:

5y = -3x + 12.

Next, divide each side by 5 to isolate y.

y = (-3x +12)/5

You can do the distributive property to get it to truly standard form, but it'll be pretty easier from here.

Pluggin' in values

I always find it helps to make a table, but however you want, find a way to record. Pick a simple value for x. Let's say 1. Your equation would look like this:

y = (-3(1) +12)/5

Work that out... -3 + 12 = 9, 9 / 5 = 1 4/5. So you have your first coordinate, (1, 1 4/5).

Try another! Let's have x = 4. So...

y = (-3(4) +12)/5

Well, -3 * 4 = 0, and 0/5 = 0, so your coordinate is (4, 0). Now that you have two points, plot them on a graph, and draw a line connecting them!
graph{y = (-3x +12)/5 [-8.89, 8.89, -4.444, 4.445]}

Jun 7, 2016

Express the equation in the point-slope form, i.e, y = mx + c.

Explanation:

3x + 5y = 12

5y = -3x + 12

y = -3/5*x +12/5

Now put values of x in the equation and get corresponding values of y. Plot the graph according to the values you get.

For example :

when x = 0, y = 12/5

when x = 1, y = 9/5

when x = -1, y = 15/5 = 3

graph{(-3/5)*x+12/5 [-7.174, 6.87, -1.386, 5.644]}