Question

help @amistre64 @ghazi

Answer 1

@jim_thompson5910

Answer 2

$$
x=a(y-\color{red}{k})^2+\color{red}{h}\ \text{ opens to the right}\\
x=-a(y-\color{red}{k})^2+\color{red}{h} \ \text{ opens to the left}\\
vertex \ is \ at (h,k)
$$

Answer 3

so, which one do you think?

Answer 4

it's opening to the left-hand-side, so "a" is negative, or -3

Answer 5

your center is (4,-3), so h = 4, k = -3
plug in the values in the standard form

Answer 6

i think its b or d

Answer 7

why don't just plug in the values? and you'll see what you get

Answer 8

is vertex anoter work for center?

Answer 9

another*

Answer 10

ohh,, yes, my bad I meant, vertex hehe, is not an ellipse

Answer 11

well, it'd be a vertex even in an ellipse, but yes, usually is called 'center' for say, a circle

Answer 12

or other figures

Answer 13

so, what did you get after you put in the values in the standard form?

Answer 14

i go with d

Answer 15

ok, so for D), what's the vertex? or (h,k)?

Answer 16

4,3

Answer 17

?

Answer 18

let's see, for a parabola whose vertex is (4,3)
$$
x=-a(y-\color{red}{k})^2+\color{red}{h} \ \text{ opens to the left}\\
x=-a(y+\color{red}{3})^2+\color{red}{4}
$$

Answer 19

does that look like D?

Answer 20

no

Answer 21

hmm, I made a tiny mistake

Answer 22

ooo what was it

Answer 23

it should be \(x=-a(y-\color{red}{3})^2+\color{red}{4}\)

Answer 24

but still

Answer 25

`ooooooooooo ok

Answer 26

your vertex given, is (4, -3), plug that into
\(x=-a(y-\color{red}{k})^2+\color{red}{h}
\)

Answer 27

what does k mean and how do i know hat number is k?

Answer 28

hehe

Answer 29

what?

Answer 30

$$
(\color{red}{h},\color{blue}{k}) \implies (\color{red}{x},\color{blue}{y})
$$

Answer 31

ooo ok

Answer 32

$$
(\color{red}{h},\color{blue}{k}) \implies (\color{red}{x},\color{blue}{y}) \implies (\color{red}{4},\color{blue}{-3})
$$

Answer 33

ooo ok so am i correct that its c?

Answer 34

well, (y-3) means (y-(+3))

as opposed to (y-(-3))

Answer 35

if that made any sense

Answer 36

lol noo i didnt get that

Answer 37

hehe

Answer 38

ok, one sec

Answer 39

ok

Answer 40

$$
(\color{red}{h},\color{blue}{k}) \implies (\color{red}{x},\color{blue}{y}) \implies (\color{red}{4},\color{blue}{-3})\\
x=-a(y-\color{red}{k})^2+\color{red}{h}\\
x=-a(y-\color{blue}{(-3)})^2+\color{red}{(4)}
$$

Answer 41

im correct then?

Answer 42

dunno, what's (y-(-3)) equal to? (y-3) or (y+3) or (y+4)?

Answer 43

you lost me there

Answer 44

ok, what's \( -1 \times -1 \)?

Answer 45

is that a multiply sign

Answer 46

yes

Answer 47

1

Answer 48

(y - (-3) )

really means

(y -1 * (-3) )

Answer 49

just like -(-2) would be 2, because -1 * -2, is just 2

Answer 50

so likewise \(x=-a(y-\color{blue}{(-3)})^2+\color{red}{(4)}\) would be ?

Answer 51

wouldnt the sign change to a posistive

Answer 52

a sign by itself outside a parentheses, is really a +1 or -1 multiplying it, thus

Answer 53

yes, the sign would change to positive, so, then
\(x=-a(y-\color{blue}{(-3)})^2+\color{red}{(4)} = x=-a(y+\color{blue}{3})^2+\color{red}{(4)} \)

Answer 54

ooooooooooooooooo

Answer 55

so, there, in this case your "a" is a "3", so, -a = -3

Answer 56

so they are bith positives

Answer 57

both

Answer 58

in this case, yes, they "k" for the "y" in standard form is negative, if you have a negative value in "k", well, -1 * -1 = +1, so :)

Answer 59

oooooo i see the answer now

Answer 60

or you can just use (y- (-3) ), which is the same

Answer 61

its A

Answer 62

:)