Question

How do you find the quadratic equation using matrices with the given points (3,91) (-1,27) (4,112)

Answer 1

@Hero i know but the teacher wants us to use matrices

Answer 2

The general form of a quadratic equation is

y = ax^2 + bx + c

Answer 3

Inputting each point in to the equation gives the following system:

91 = 9a + 3b + c
27 = a - b + c
112 = 16a + 4b + c

Answer 4

what do you do after that then?

Answer 5

First you'll have to rewrite the system like so

9a + 3b + c = 91
a - b + c = 27
16a + 4b + c = 112

Then treat a, b, c as the variables and the numbers as the coefficients.

Answer 6

this whole concept is very confusing to me. This extra credit assignment is worth about half of a test so i really want to get this right.

Answer 7

Then you can setup the matrix. Only thing is, you'll run into a problem while solving.

Answer 8

what problem?

Answer 9

Actually, they probably mean for you to solve this using Cramer's Rule like that link @zzr0ck3r provided

Answer 10

http://www.algebra.com/algebra/homework/quadratic/Quadratic_Equations.faq.question.448999.html

Answer 11

oh okay. Thanks then!

Answer 12

Someone posted this same exact question about a week ago and no one could figure it out. They said "Solve using matrices" instead of "Solve using Cramer's Rule"
In a way, it's a trick question, but not really.

Answer 13

Just a different name? Probably the same class as me haha.

Answer 14

When a question says "Solve using matrices", Cramer's Rule isn't the first thing that comes to mind.

Answer 15

But from now on, you can be on the lookout for such questions.

Answer 16

Oh.
What?

Answer 17

A large percentage of math questions are structured this tricky way where it seems unfamiliar, but with a bit more creative thought, you can think of the right approach to answering it.

Answer 18

THANK YOU MAN

Answer 19

@jayz657, do you have anything you wish to contribute?

Answer 20

oh sorry i was afk from open study but nope everything is all good :)