Pre-Calc

[LkptTiger 1]

Well, as you have probably gathered, I am having some difficulties with my new Pre-Calc teacher. He spends most of his time focusing on and talking to the two or three seniors in my class (the other 10 or so of us are accelerated juniors) and does an extremely shitty job explaining what needs to be done. Needless to say, just about all of us are confused. I realize that most of this stuff is "review" but as this is the third week of school, we don't really have any idea what the Hell is going on.

The homework tonight (he breezed through a few problems, but didn't explain them at all.

Basically, they look like this -

{x+y=5}

{x-y=3}

It says that we need to use the addition or the subtraction method to solve for x and y. These aren't matricies (if they were I wouldn't be having these issues). I feel like a complete moron for asking for help,which means that I really, really have no clue as to what is going on. Thanls for any help you fellas can offer me.

[Perry94 0]

you know what...I'm in the same boat...my calc teacher can't teach worth s#$t...

[crosskore 0]

{x+y=5}

{x-y=3}

x=y+3

(y+3)+y=5

y+3+y=5

2y=-3+5

2y=2

y=1

x=y+3

x=1+3

x=4

check answer

x+y=5?

1+4=5

therefore x=4 and y=1

If this looks like what you needto do, just reply and I'll explain how i did it. If you want, you can add meto msn Kornography_6@hotmail.com or AIM james14jester.

Iam pretty sure thats what your suppose to do. looks right to me, it think you call it "addition and subtraction" and we call it "elimination and substitution" in canada, but its the same thing. your doing graphing as well, am i right?

[LkptTiger 1]

GOOD MAN!

Yeah, that looks vaguely familiar. Thanks, buddy. I'll see if I can't put that and what little I have learned thus far into getting all this stuff done. Thanks again, you're the man ;)

[crosskore 0]

{x+y=5}

{x-y=3}

^^^^these are yout two original formulas.

x=y+3

^^^^ You haveto choose one formula to change into x= or y=. As you can see, I chose the second one and I chose to declare the X value. to get the X by itself, i hade to move the Y over, witch changed it from a "-y" neggative, to a posative, because its now on the other side of the = sign. so now you have x=y+3.

(y+3)+y=5

^^^^^^^^ After that, you substitue your new X value. I chose to sub it into the first formula. so instead of x+y=5, we dont put "x" because you can see above, we declared x=y+3. so where X goes, you put y+3, thats how you get (y+3)+y=5

y+3+y=5

^^^^^^ Simplify it by taking away the brakets.

2y=-3+5

^^^^^^ the two y's add together to make 2y. you have to isolate the y value, so movethe 3 over to the other side, that changes it from a posative to a negative. thats how i got 2y=-3+5

2y=2

^^^ do the math. you want to know what Y is, not 2y, so you divie 2y by two,what you do to the left, you do to the right, so you divide 2 by 2. so it would be 2y/2=2/2

y=1

^^^ you get that.

Now to get X, you simply take the original equation, and where it says "y" you put in 1

x+y+3

x+1+3

x=4

Then to check your answer, you take the original equation, and put the answer for x andthe answer for y where it says y and x.

check answer

x+y=5?

1+4=5

therefore x=4 and y=1

nowthats only one of the two ways. if you need help with the other way, I will be more then happy to help. I actualy have a test on all of this stuff this week sometime, so it helps me too :)

[LkptTiger 1]

If you could help me with the other way (apparently my teacher chooses to call it "addition") that would be great, since we got twelve of each for homework tonight. You've been a huge help. I really appreciate it...Now if I could find a way to pump all of those pills I swallowed earlier out of my stomach I'll really be in business ;)

{2x+y=7}

{2x-y=1}

Thanks again, bud.

[crosskore 0]

{2x+y=7}

{2x-y=1}

Ok, this other way is pretty simple. you have the x's and the y's lined up

{2x+y=7}

{2x-y=1}

most questions already do that for you, as you can see, the x in the first equation is right above the x in the second equation. the object is to "eliminate" either the x or the y values by "adding". to do this, you need to have the x or y value (what ever you decide to eliminate) on the top and the botom to be different signs( top one be a posative, bottom be a negative, or other way around) as well as being the same number.

{2x+y=7}

{2x-y=1}

Asyou can see, in the first equation, we have a +y and in the second we have a -y. so they already did a step for you. first you take your two eqations and add the "like" values (the x's in the first equation and the x's inthe second and so on).

{2x+y=7}

+

{2x-y=1}

=

4x=8

^^^^ because the -y and the +y cancel out.

now just just divide 4x by 4, to get the singel x. and beause you divided that side by 4, you haveto divide the right side by 4. so, 4x/4=8/4

x=2

Now to find the Y value, you do the same thing you did in the other one I showed you. just sub 2 where X goes. so.

2x-y=1

2(2)-y=1

4-y=1

^^^^ then you have to gey Y by itself, so move 4 over, because you moved it over, it goes from a posative to a negative.

-y=-4+1

-y=-3

^^^ now divde -y by -1, because you want a posative value, not negative. although it says -y, it really means -1y.... they just dont show the 1, because its understood that its there.

-y/-1=-3/-1

y=3

Now to check, you just take an original equation and sub in.

2x+y=7

2(2)+3=7?

4+3=7

now, just to let you know they had that one set up for you already.

{2x+y=7}

{2x-y=1}

pretend the question was

2x+y=7

2x+4y=7

^^^^^^ noticeyou dont have two variables that are the same number, and opposite signs, so you would have to multiply one(or both sometimes) ofthe equations to make it like that. we already have the X's as the same number, but if you add 2+2 it =4 not 0, you need it to = 0, so.... pick one ofthe equations and multiply it by -1. Lets pick the top one. you have to multiply EVERY number by -1.

2x+y=7 new equation is -2x-y=-7

2x-y=1

so now, we have a 3rd equation. now you just go

-2x-y=-7

+

2x-y=1

= -2y+-6

Now you just do the same thing as you did above.

Now, if the equation was

3x-7y=7

2x-5y=1

you have to have two variables the same with opposite signs right? so pick a variable(lets pick x) and find a common multiplier. 6 is a multipliers of both 3 and 2. so, to get the first equations X to=6 you multiply by 2 (2 times 3=6) so you multiply the WHOLE equation by 2. the second equation has to be multiplied by 3, for the X to be 6. but remember, we need one negative and one posative, so lets multiply the second one by -3 instead of just 3.

your new equations will be

6x-14y=14

+

-6x+15y=-3

=

1y=11

now just go on like usual.

[foppa21 0]

I'm sorry to hear that you have a crappy teacher dude. My senior Pre-calc teacher last year was the best math teacher that I've ever had.

[Stampeder 2]

My applied math teacher this year is crazy, 1 hour of math homework a night. I haven't did it once.

[crosskore 0]

Homework is something I hate. All I do is do the first couple questions to makesure i understand it, then do the last question (usualy the hardest) then I check to see if it right and if it is a stop. I change 1 hour of homework to 15 mins. theres no point of doing it over and over again if you understand it, thats what makes you hate it. if you dont understand it though, then do the homework.

[Jackal3688 0]

Just wait til calc next year ;) . I'm a junior in AP calc, and just like you, my teacher is terrible. Well, enjoy it while it lasts, and pray you get a really good teacher next year for calc, or else youre screwed like me lol.

[BobEP 0]

This is Pre-Calc??? I learned all this in 8th grade, they are simple algebraic equations...

[foppa21 0]

The first part of Pre-Calc is a bunch of algebra I and II review.

[LkptTiger 1]

This is Pre-Calc??? I learned all this in 8th grade, they are simple algebraic equations...

...Remember that this is September, which means that my brain has been pretty much hibernating for the last three months or so. With all this math stuff along with the work I am getting in all the other AP courses and hockey practice five or six nights a week, I'm on overload right now.

The "best" part about this great big pile of shit I have infront of me is that this new teacher of mine (oh how I loathe this "man") is my first new math teacher I have had since 8th grade. My last teacher, who was a great guy and a really good teacher, has been with myself and the rest of the "accelerated" students through our 8th, 9th and 10th grade years. I have heard many horror stories about the guy I now have, but I never thought it would be this bad. The guy who sits behind me (also accelerated) mumbles "I'm going to kill him. That's it, I'm going to kill him. I can't stand this guy..." etc. for pretty much the entire period. Yes, it is that bad.

[ambro 0]

My applied math teacher this year is crazy, 1 hour of math homework a night. I haven't did it once.

Doesn't look like you've been doing your English either... ;)

[Stampeder 2]

Next semister;)

[crosskore 0]

Did my online teaching help at all? Its hard to explain over the internet.

[LkptTiger 1]

Did my online teaching help at all? Its hard to explain over the internet.

Absolutely. Hell, I learned more in the five or ten minutes I was reading your posts then I probably would the entire year. I REALLY appreciate it.

Just an example of how incredibly insane and rediculous this teacher is...Today, at the end of "class," he told us that we would not be needing our books or binders tomorrow; that, for the entire 42 minutes of "class" tomorrow he will be reading us a book (WTF?) entitled Who Moved My Cheese. Apparently it will help us cope with any future problems that we may encounter . After the reading of this book, we will be told to write a five page essay in which we are supposed to state which character we can most identify with. Keep in mind, this is Pre-Calculus. I came into this "class" three weeks ago expecting five pages of equations a night. Since then, we have been assigned three projects that I would expect to be given in my IAP English class...

[SLy MaLLone 0]

I think one of the speakers at my High School graduation read that story during our ceremony.