Graph 9x^2+y^2=9

$9 x^{2} + y^{2} = 9$

Step 1

Find the standard form of the ellipse.

Divide each term by $9$ to make the right side equal to one.

$\frac{9 x^{2}}{9} + \frac{y^{2}}{9} = \frac{9}{9}$

Simplify each term in the equation in order to set the right side equal to $1$ . The standard form of an ellipse or hyperbola requires the right side of the equation be $1$ .

$x^{2} + \frac{y^{2}}{9} = 1$

Step 2

This is the form of an ellipse. Use this form to determine the values used to find the center along with the major and minor axis of the ellipse.

$\frac{{(x - h)}^{2}}{b^{2}} + \frac{{(y - k)}^{2}}{a^{2}} = 1$

Step 3

Match the values in this ellipse to those of the standard form. The variable $a$ represents the radius of the major axis of the ellipse, $b$ represents the radius of the minor axis of the ellipse, $h$ represents the x-offset from the origin, and $k$ represents the y-offset from the origin.

$a = 3$

$b = 1$

$k = 0$

$h = 0$

Step 4

The center of an ellipse follows the form of $(h, k)$ . Substitute in the values of $h$ and $k$ .

$(0, 0)$

Step 5

Find $c$ , the distance from the center to a focus.

Find the distance from the center to a focus of the ellipse by using the following formula.

$\sqrt{a^{2} - b^{2}}$

Substitute the values of $a$ and $b$ in the formula.

$\sqrt{{(3)}^{2} - {(1)}^{2}}$

Simplify.

Raise $3$ to the power of $2$ .

$\sqrt{9 - {(1)}^{2}}$

One to any power is one.

$\sqrt{9 - 1 \cdot 1}$

Multiply $- 1$ by $1$ .

$\sqrt{9 - 1}$

Subtract $1$ from $9$ .

$\sqrt{8}$

Rewrite $8$ as $2^{2} \cdot 2$ .

Factor $4$ out of $8$ .

$\sqrt{4 (2)}$

Rewrite $4$ as $2^{2}$ .

$\sqrt{2^{2} \cdot 2}$

Pull terms out from under the radical.

$2 \sqrt{2}$

Step 6

Find the vertices.

The first vertex of an ellipse can be found by adding $a$ to $k$ .

$(h, k + a)$

Substitute the known values of $h$ , $a$ , and $k$ into the formula.

$(0, 0 + 3)$

Simplify.

$(0, 3)$

The second vertex of an ellipse can be found by subtracting $a$ from $k$ .

$(h, k - a)$

Substitute the known values of $h$ , $a$ , and $k$ into the formula.

$(0, 0 - (3))$

Simplify.

$(0, - 3)$

Ellipses have two vertices.

${Vertex}_{1}$ : $(0, 3)$

${Vertex}_{2}$ : $(0, - 3)$

${Vertex}_{1}$ : $(0, 3)$

${Vertex}_{2}$ : $(0, - 3)$

Step 7

Find the foci.

The first focus of an ellipse can be found by adding $c$ to $k$ .

$(h, k + c)$

Substitute the known values of $h$ , $c$ , and $k$ into the formula.

$(0, 0 + 2 \sqrt{2})$

Simplify.

$(0, 2 \sqrt{2})$

The first focus of an ellipse can be found by subtracting $c$ from $k$ .

$(h, k - c)$

Substitute the known values of $h$ , $c$ , and $k$ into the formula.

$(0, 0 - (2 \sqrt{2}))$

Simplify.

$(0, - 2 \sqrt{2})$

Ellipses have two foci.

${Focus}_{1}$ : $(0, 2 \sqrt{2})$

${Focus}_{2}$ : $(0, - 2 \sqrt{2})$

${Focus}_{1}$ : $(0, 2 \sqrt{2})$

${Focus}_{2}$ : $(0, - 2 \sqrt{2})$

Step 8

Find the eccentricity.

Find the eccentricity by using the following formula.

$\frac{\sqrt{a^{2} - b^{2}}}{a}$

Substitute the values of $a$ and $b$ into the formula.

$\frac{\sqrt{{(3)}^{2} - {(1)}^{2}}}{3}$

Simplify the numerator.

Raise $3$ to the power of $2$ .

$\frac{\sqrt{9 - 1^{2}}}{3}$

One to any power is one.

$\frac{\sqrt{9 - 1 \cdot 1}}{3}$

Multiply $- 1$ by $1$ .

$\frac{\sqrt{9 - 1}}{3}$

Subtract $1$ from $9$ .

$\frac{\sqrt{8}}{3}$

Rewrite $8$ as $2^{2} \cdot 2$ .

Factor $4$ out of $8$ .

$\frac{\sqrt{4 (2)}}{3}$

Rewrite $4$ as $2^{2}$ .

$\frac{\sqrt{2^{2} \cdot 2}}{3}$

Pull terms out from under the radical.

$\frac{2 \sqrt{2}}{3}$

Step 9

These values represent the important values for graphing and analyzing an ellipse.

Center: $(0, 0)$

${Vertex}_{1}$ : $(0, 3)$

${Vertex}_{2}$ : $(0, - 3)$

${Focus}_{1}$ : $(0, 2 \sqrt{2})$

${Focus}_{2}$ : $(0, - 2 \sqrt{2})$

Eccentricity: $\frac{2 \sqrt{2}}{3}$

Step 10

Graph 9x^2+y^2=9

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