Steply

Which conic is x^2 - 4y^2 = 4

Step by step, with the reason for every step · Conics from the general form · Precalculus

Step by step

The question

Question: name the conic and write in standard form x² − 4y² − 4 = 0.

x2 − 4y2 − 4 = 0

1 Name the conic

Look at the squares.

x² and y² have different signs.

So it is a hyperbola.

only x² or only y² → parabola
x² and y², same number in front → circle
same signs, different numbers → ellipse
different signs → hyperbola ✓

2 Move the number

Move the plain number to the right: − 4 becomes + 4.

x2 − 4y2 = 4

3 Make the right side 1

Divide every part by 4, so the right side is 1.

4/4 is 1/1.

x24 − y2 = 1
4 ÷ 1 = 4, 4 ÷ −4 = -1

That is the standard form of a hyperbola with center (0, 0).

hyperbola: center (0, 0)

4 Check

Let's check with a point on it: (2, 0), a vertex.

Put it in the first equation.

2² − 4 × 0² − 4 = 4 + 0 − 4 = 0

We get 0, like the first equation says.

So the standard form is right!

Let's look back.

First: name the conic.

Then: move the number.

Then: make the right side 1.

Last: check.

Answer
4 ÷ 1 = 4, 4 ÷ −4 = -1

Your turn

Try this one yourself, then check:

Name the conic and write in standard form x2 − 9y2 − 9 = 0
Show the answer
x29 − y2 = 1

More from Conics from the general form

The whole lesson: Conics from the general form →