Question

Need some help!

Answer 1

Graph 4x2 + y2 = 9. What are its lines of symmetry?

Answer 2

@hartnn @phi @ZeHanz @zepdrix

Answer 3

I would divide both sides by 9

\[ \frac{4 x^2}{3^2} + \frac{y^2}{3^2} = 1\]
or, changing multiplying by 4 to dividing by 1/4
\[ \frac{x^2}{\frac{3^2}{2^2}} + \frac{y^2}{3^2} = 1\]
or
\[ \frac{x^2}{\left(\frac{3}{2}\right)^2} + \frac{y^2}{3^2} = 1\]

Answer 4

oh ok... but how does the graph look?

Answer 5

that form should ring bells
See http://www.mathwarehouse.com/ellipse/equation-of-ellipse.php

Answer 6

would it be every line through orgin is line of symmetry
or It has two lines of symmetry: the x axis and the y- axis
@phi

Answer 7

does anyone else know

Answer 8

this is an ellipse

Answer 9

I know what graph looks like but which is it

Answer 10

it looks symmetric about the x and y axes
(i.e. left side = mirror image of right side. same for top and bottom)

Answer 11

oh ok so B.?

Answer 12

if B means x and y axes

Answer 13

this is B. ----> It has two lines of symmetry: the x axis and the y- axis

Answer 14

yes, that looks good

Answer 15

thank!

Answer 16

could you help on one more

Answer 17

What are the focus and the directrix of the graph of x = 1/24y^2?

Answer 18

anyone?

Answer 19

write it as
y^2 = 24x and match this to the form
y^2 = 4px

so you have
y^2 = 4* 6*x
p is 6

Answer 20

does that mean the diretix is 6

Answer 21

or part of the focus??

Answer 22

the 6 means the focus is 6 in from the vertex
and the directrix is 6 in the opposite direction

Answer 23

so focus would be (6,0)

Answer 24

directix =
x=-6??

Answer 25

yes, that sounds right.

Answer 26

ok!

Answer 27

why wouldn't it be (0,6)

Answer 28

You have to know which way the parabola is opening up.

Answer 29

so u are sure its (6,0)

Answer 30

one way to figure it out is write
y^2 = 4* 6*x
as
y = ± sqrt(24 x)

x has to be positive (or you get imaginary values)
y will be + and - the same value
so it should look like this

the focus will have y=0 and some x value