Steply

Graph y > 2x - 1

Step by step, with the reason for every step · Graphing inequalities · Algebra 1

Step by step

The question

Question: graph y > 2x − 1.

y > 2x − 1

The answer is not one point.

It is every point that makes this true.

That is a whole part of the grid.

answer = all the points that work

1 Draw the line

First we draw the line where both sides are equal: y = 2x − 1.

y = 2x − 1

The sign is more than, with no "or equal to".

So points on the line are not answers.

We draw it dashed, like the open circle on a number line.

> → dashed line

Draw the grid.

The x-axis goes across.

The y-axis goes up and down.

They meet at 0.

That point is called the origin.

b = −1.

Start on the y-axis at −1.

m = 2.

As a fraction: 2/1.

Go right 1,

then up 2.

Dot.

Join the dots: dashed.

2 Test a point

The line cuts the grid in two sides.

One side is the answer.

We test one point: (0, 0).

Zeros are easy to work with.

Put x = 0 and y = 0 in.

0 > 2(0) − 1
0 > −1 true

Is 0 more than −1?

Yes, that is true.

So (0, 0) is an answer.

3 Shade

So we shade the side with (0, 0).

Every point there is an answer.

4 Check

Let's check with a point in the shaded part: (−2, −1).

Put x = −2 and y = −1 in.

−1 > 2(−2) − 1
−1 > −5 true

True!

So the shading is right.

Let's look back.

First: draw the line.

Then: test a point.

Then: shade.

Last: check.

Answer
0 > −1 true

Your turn

Try this one yourself, then check:

Graph y > 3x − 1
Show the answer
dashed line y = 3x − 1, shade above

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