Which quadratic rule represents the data in the table??

Question

anonymous · Answer

attachment

thesmartone · Answer

Plug in the x-values in to each answer choice. If it gets the correct y-value then it is your correct equation.

thesmartone · Answer

So, if you plug in x=-1

you should get y=4

anonymous · Answer

I tried that it didn't work :/

anonymous · Answer

@TheSmartOne

thesmartone · Answer

Try it for each answer choice.

thesmartone · Answer

And then plug in another point into whatever answer choices remain to get the final answer.

anonymous · Answer

I did try multiple times.. Did you get it with one of them?

thesmartone · Answer

Yes.

anonymous · Answer

They aren't matching though. Like it doesn't equal y on the table.

thesmartone · Answer

Ok, let me show you how to do it.

$\sf y=-2x^2+5$
Plug in x=-1 and y= 4

$\sf 4= -2(-1)^2+5$
$\sf 4= -2(1)+5$
$\sf 4 = -2 + 5$
$\sf 4 \neq -3$

So A is incorrect.

anonymous · Answer

Ooooh I don't think I was following PEMDAS... hold on

anonymous · Answer

nevermind

anonymous · Answer

still wrong

thesmartone · Answer

A is wrong.

Do what I did for the other 3 equations.

You should get that two equations will work for one point. Then you have to plug in another point to eliminate...

thesmartone · Answer

Also, show your work so I can see where you are messing up...

anonymous · Answer

Okay

anonymous · Answer

So for y= x^2 - 5
I do -1^2 which is  1 then 1-5 = -4 which isn't right.

anonymous · Answer

y = x^2 + 5 
1 + 5 is 6.

anonymous · Answer

(because -1^2 again is 1)

thesmartone · Answer

good job so far. One last equation left. :)

anonymous · Answer

Since it's already negative what am I to do? Would it be positive?

anonymous · Answer

I tried doing both but got nothing

thesmartone · Answer

Well, since all the other 3 are correct, this one has to be correct.

anonymous · Answer

How? It's not correct I'm getting 6.

thesmartone · Answer

But the way to do it is:

$\sf\large y=-x^2+5$

Plug in x=-1 and y=4

$\sf\large 4 = -1 ( -1)^2+5$

anonymous · Answer

You did -1 twice?

thesmartone · Answer

$\sf -x^2 = -1 \times x^{2}$

anonymous · Answer

that's still -1 though.

thesmartone · Answer

$\sf\large y = -x^2+5$

Ok, again :P

Plug in x=-1 and y=4
 
$\sf\large 4 = -(-1)^2+5$

anonymous · Answer

I'm getting 6 though.

thesmartone · Answer

$\sf\large 4 = -(-1)^2+5$

$\sf\large 4 = -(1)+5$

$\sf\large 4 = -1+5$

$\sf\large 4 = 4$

anonymous · Answer

Oooh haha

anonymous · Answer

Sorry. I don't know I guess I just looked at it wrong.

anonymous · Answer

Thanks for being patient with me ^.^

thesmartone · Answer

Yea, the negative can confuse some people.

thesmartone · Answer

But practice makes perfect. c:

anonymous · Answer

:)

thesmartone · Answer

Thanks for cooperating (:

anonymous · Answer

Thank you again! :)

thesmartone · Answer

:)