Question

I need help with a multiple choice question.. (will MEDAL and FAN)

Answer 1

What is your question? I can try...

@LetsLearn2000

Answer 2

@AihberKhan here it is & thanks! Appreciate all help. :)

Answer 3

Sorry, I am not very good with parabolas. This link might help you because it is similar to your question:

http://www.algebra.com/algebra/homework/quadratic/Quadratic_Equations.faq.question.112182.html

Sorry again! :)

@LetsLearn2000

Answer 4

i wanna say B but im not good with that lol

Answer 5

@mathmale lend a hand?

Answer 6

The standard equation of a parabola, which is one of the simplest forms, is
\[y=a(x-h)^2 + k,\],
where a is a constant coefficient and (h,k) represents the vertex of the parabola.

Your unknowns here are a, h and k.

You have 3 points which supposedly line on the parabola.
As the rule goes: Three equations in three unknowns is a situation solvable for those unknowns.

Answer 7

Ok.. would you mind taking me through it

Answer 8

@jim_thompson5910

Answer 9

Right off the bat you can eliminate 2 answer choices. How? By looking at the point (0,-4.5) which is the y intercept. If x = 0, then the majority of y = ax^2+bx+c will go away leaving y = c as the only thing left over

so if y = -4.5 from the y intercept, then y = c leads to c = -4.5

only A and C fit if c = -4.5

Answer 10

Ok I see what you did, thanks Jim. C it is lol.

Answer 11

Expanding what I mean by `If x = 0, then the majority of y = ax^2+bx+c will go away leaving y = c as the only thing left over`

y = ax^2+bx+c

y = a*0^2+b*0+c ... replace x with 0

y = a*0 + b*0 + c

y = 0 + 0 + c

y = c

Answer 12

to see which one it is (A or C), simply test another point given. So either (-2, -23.5) or (4, -26.5)

Answer 13

wait.. or is it A

Answer 14

if you picked (-2, -23.5) , then the idea is that plugging in x = -2 should lead to y = -23.5

one of the functions (A or C) does this

Answer 15

hopefully that makes sense?

Answer 16

yes it does let me do it really quick then tell me if I'm correct or not

Answer 17

ok So its most Def not the one with -2 because I swapped X for -2 in the "C" equation and got -17.5

Answer 18

you mean you plugged x = -2 into the equation for choice C and you got y = -17.5 ?

Answer 19

basically.

Answer 20

ok try choice A now

Answer 21

I got -23.5 for choice A so that must be it

Answer 22

choice A is definitely the answer. I recommend you also try plugging in x = 4 and seeing if that same equation produces y = -26.5 or not. This is to confirm ALL 3 points are on this parabola

Answer 23

I just did and I got -26.5 so thats it. Thanks for the help

Answer 24

no problem

Answer 25

Jim's approach was appropriate and a lot faster and simpler than mine. Nice insight, Jim!

Answer 26

the approach only works if you have a set of choices to work with

if you don't have any answer choices, then it's best to use the method shown in the link AihberKhan posted