Rev7 Posted October 3, 2008 Share Posted October 3, 2008 Yeah, I don't want to be spamming the Math is Cool thread so I thought that I should make this. Well, ya I need some help with my math homework. ASAP would be helpful...<snip> I just need help Solve by using elimination: 8x+3y+5=0 10 x+6y+13 and: x/4-y/3=1 1/3x-4y/9=4/3 I would greatly appretiate any help... Link to comment Share on other sites More sharing options...
Rabish Bini Posted October 3, 2008 Share Posted October 3, 2008 I'd love to help but I don't think I understand the question correctly... Link to comment Share on other sites More sharing options...
Inyri Posted October 3, 2008 Share Posted October 3, 2008 If you "mainly just forgot" then just check that section in your text book. Link to comment Share on other sites More sharing options...
Rev7 Posted October 3, 2008 Author Share Posted October 3, 2008 Okay. Example: 2x+y=1 3x-y=14 Show spoiler (hidden content - requires Javascript to show) Work: 5x=15 x=3 2(3)+y=1 6+y=1 -6 -6 y=-5 Final Answer: (3,-5) This is on my homework, and I have no one to help me. I have attemped them, but am a little stuck and need some help. That is all. Link to comment Share on other sites More sharing options...
Rabish Bini Posted October 3, 2008 Share Posted October 3, 2008 10 x+6y+13 I think you left out the answer for this one Link to comment Share on other sites More sharing options...
Rev7 Posted October 3, 2008 Author Share Posted October 3, 2008 ^ sorry... 8x+3y+5=0 10 x+6y+13 Show spoiler (hidden content - requires Javascript to show) (-3) 8x+3y+5=0 = -24x-6y-15=-3 ___ -24x-3y-15=-3 + 10 x+6y+13=0 _____________________ -14x-2=-3 -14x=-1 This is where I am stuck. If you "mainly just forgot" then just check that section in your text book. It is on a worksheet. EDIT: I see my mistake in that...fixed...still stuck though Link to comment Share on other sites More sharing options...
Inyri Posted October 3, 2008 Share Posted October 3, 2008 I understand it's a worksheet. Pull out your book and read that section. If you didn't bring your book home with you to do your homework, take this as your lesson learned. Link to comment Share on other sites More sharing options...
Rev7 Posted October 3, 2008 Author Share Posted October 3, 2008 My teacher gaves us notes, and explained how to do it and I understand how to do it...it is just that I am stuck on these problems. Link to comment Share on other sites More sharing options...
HerbieZ Posted October 3, 2008 Share Posted October 3, 2008 Math only taught me one thing. If the guy is using letters instead of numbers to work out the bill, punch him in the face. Link to comment Share on other sites More sharing options...
Rabish Bini Posted October 3, 2008 Share Posted October 3, 2008 Math only taught me one thing. If the guy is using letters instead of numbers to work out the bill, punch him in the face. They're know as Pro-numerals, punching him in the face seems like the logical thing to do I'm trying to figure out the answers Rev7, but I'm a bit stuck as to the answer in the second line of the first question, I do believe there's supposed to be an answer there, or am I missing something? Link to comment Share on other sites More sharing options...
Rev7 Posted October 3, 2008 Author Share Posted October 3, 2008 10x+6y+13=0 I forgot the zero, I think. My bad... Link to comment Share on other sites More sharing options...
Arcesious Posted October 3, 2008 Share Posted October 3, 2008 And you said you would have the skills to help me if I needed help, lol. Your math looks slightly more advanced than what I'm at at the moment. My Algebra class is doing those same kinds of equations, and tommorw is when I bet we'll be using fractions... Although I think I understand this already... My advice: Eliminate the smallest variable term first. Example: 7n-2=5n + 6 -5n -5n 2n - 2 = 6 + 2 + 2 2n = 8 /2 /2 n = 4 In this, the variable is n. one side had 7n, one side has 5n. You get rid of the lesser variable first. I got rid of 5n first. As for negative variables and positive variables - get rid of the negative variable first. (or the negative variable farthest from 0) Think of integers. Anything less than 0 is smaller than anything more than 0... IE: for -5n and -7n, -7n is the smaller variable term. Link to comment Share on other sites More sharing options...
Inyri Posted October 3, 2008 Share Posted October 3, 2008 That works fine if there's only one variable. His work has two different variables. Link to comment Share on other sites More sharing options...
Arcesious Posted October 3, 2008 Share Posted October 3, 2008 That works fine if there's only one variable. His work has two different variables. Oh... I can't brain today, I have the dumb. lol. Forget what I said Rev7... I guess I actually have no idea how to do what you're doing there... Link to comment Share on other sites More sharing options...
Rev7 Posted October 3, 2008 Author Share Posted October 3, 2008 What we are doing is solving systems of equations Algebraically. Eventually we will make graphs with them. This is a review for me, it is just it has been a good year before I last did something like this and I got stuck. Today's homework is/was on the hard side. @Arc--what you were doing is correct, my equations are just a little bit more....advanced/harder/have more steps...I understand what you are doing. Link to comment Share on other sites More sharing options...
Boba Rhett Posted October 3, 2008 Share Posted October 3, 2008 Solve for 3y and then substitute in the second line: 8x + 3y + 5 = 0 10x + 6y + 13 = 0 => first line = 3y = -8x - 5 So Second line equals, 10x + 2(-8x - 5) + 13 = 0 10x + -16x - 10 + 13 = 0 -6x + 3 = 0 -6x = -3 6x = 3 x = .5 Test: 4 + 3y + 5 = 0 3y = -9 y = -3 Test: 10(.5) + 6(-3) + 13 = 0 5 + -18 + 13 = 0 => True Link to comment Share on other sites More sharing options...
Da_man Posted October 3, 2008 Share Posted October 3, 2008 Dammit Rhett beat me to it. It's Systems of Equations' right? Link to comment Share on other sites More sharing options...
tk102 Posted October 3, 2008 Share Posted October 3, 2008 (-3) 8x+3y+5=0 = -24x-6y-15=-3 False... 8x + 3y + 5 = 0 x -3 ------------ -24x -9y -15 = 0 Hint: Try -2 instead of -3... then add the two equations to eliminate the y variables. Link to comment Share on other sites More sharing options...
Boba Rhett Posted October 3, 2008 Share Posted October 3, 2008 Good lord, I dunno. Do you have any idea how much Sudafed is in me right now? I just do maths. Link to comment Share on other sites More sharing options...
Litofsky Posted October 3, 2008 Share Posted October 3, 2008 If I remember this type of equation correctly, as tk mentioned, you 'line up' the equations, eliminate one of the two variables, and go to town. Example: 5x+2y=5 x+3y=-7.5 Now, since none of the variables are equal, we need to make 'em equal. So, let's try to get the "x" variables equal. 5x+2y=5 (NOTE: in order to get the "x"s equal, we need to multiply this equation by -5. -5, so that the two will cancel out [-5+5=0]Therefore...) x(-5)+3(-5)y=-7.5(-5) Now simplified: 5x+2y=5 -5x-15y=37.5 "X"s cancel out... 2y=5 -15y=37.5 Now, if I did that correctly, "y" should equal 2.5 Go back into the equation, plug "y" in, and you should be able to solve the one-variable equation. I hope that helps. Link to comment Share on other sites More sharing options...
Inyri Posted October 3, 2008 Share Posted October 3, 2008 I prefer solving for Y and making the equations equal, but I don't think that's 'solving by elimination.' Link to comment Share on other sites More sharing options...
Litofsky Posted October 3, 2008 Share Posted October 3, 2008 I prefer solving for Y and making the equations equal, but I don't think that's 'solving by elimination.' Maybe it isn't. It's been a while since I've done this, so I might have remembered incorrectly. Link to comment Share on other sites More sharing options...
Inyri Posted October 3, 2008 Share Posted October 3, 2008 I dunno, this is the bit I always hated about math. Having to do something a 'certain way' when it's obviously not the best way. Link to comment Share on other sites More sharing options...
Nedak Posted October 3, 2008 Share Posted October 3, 2008 Oh you're solving for X. I'd do it but I don't remember stuff from 8th grade (that's when I learned it). Link to comment Share on other sites More sharing options...
Boba Rhett Posted October 3, 2008 Share Posted October 3, 2008 You dun remember teh algebras? Link to comment Share on other sites More sharing options...
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