Question

Ralph wants to find the solution to a system of equations using y = x - 4 and y = x2 + 2x - 46. Molly says that Ralph can solve x2 + x - 42 = 0 to find the x coordinates of the solutions to his system. Explain and demonstrate why Molly is correct.
@halorazer @PhysicsGuru

Answer 1

Not going to give you the answer, we you have two equation you can add,subtract,multiply them .... try one of these operations and you will find the answer

Answer 2

-7?

Answer 3

You have to perform one of these operations to prove Molly is correct so you are looking to get x2 + x -42 = 0

Answer 4

What he's saying is what do you do with x-4 and x^2+2x-46 to reach x^2+x-42.

Answer 5

so im going to use subsituition is that alright

Answer 6

i dont get it what do you have to do to get that?

Answer 7

Try what you just stated

Answer 8

now im confused there no Y in the equation

Answer 9

that is fine you are proving this equation x2 + x -42 = 0

Answer 10

yeah i know but how would i write it

Answer 11

Look at how it is written and what you have now after the substitution.. you want to setup both sides to look like the above equation

Answer 12

ohhhhhhhhhhhhh so i have to elminate the Y variable?!!?!?

Answer 13

yes

Answer 14

x - 4=x2 + 2x - 46 is this how it would look

Answer 15

yes

Answer 16

what do you call this method?

Answer 17

@PhysicsGuru

Answer 18

You substituted for y with x-4

Answer 19

so do i move everything to the left or right?

Answer 20

You have to try what you think and stop looking at others for step by step for all problems because the test later will hurt your grade then.... try it!!

Answer 21

Guru I know this is why Im practicing with you. im going to move it to the right alright? i jsut need you to tell me if thats right so i dont wast time thats all :)

Answer 22

It is not a waste of time if you get the wrong answer ... that is learning!! however if you look to others for clarification then you will always doubt yourself. I am a teacher and this is what students will do because they are afraid of incorrect answers.

Answer 23

Thanks! ok i will let you know how far i get

Answer 24

x=x^2 + 2^x - 42

Answer 25

@PhysicsGuru

Answer 26

do we make those thingys with two equations?

Answer 27

factor i mean?

Answer 28

@nincompoop pls help me?

Answer 29

sure

Answer 30

do you want from the very basic idea of systems of linear equations?

Answer 31

yeah

Answer 32

when two lines are involved in a cartesian graph, we can make certain predictions at what point those two lines may intersect or not intersect at all.