LukasMcNeal Posted September 10, 2012 Report Share Posted September 10, 2012 Basically I have an inital task for college, I havent done this sort of maths for a while because of my apprenticeship but now im back at college. to be honest im stunned and im going to explain to my teacher I need to go back to basics a bit but can someone explain in a hope ill remember or atleast make me understand a bit! The equation is 6x^2 - 7x - 10 = 0 and it says to solve by graphing, factorisation and formula. Any help would be great and no im not gonna just copy it and hand it in im going to ask for the help! Quote Link to comment Share on other sites More sharing options...
Revolver Posted September 10, 2012 Report Share Posted September 10, 2012 (edited) I got the square root of 10 If that's right I'll pat myself on the back, I have no idea what I'm doing, really. Edited September 10, 2012 by Revolver Quote Link to comment Share on other sites More sharing options...
Simpson Posted September 10, 2012 Report Share Posted September 10, 2012 Basically to get the 6x^2 term using simple factorisation there are 2 ways to achieve this (unless you take out the 6). In this example y and z are still unknown variables. (6x + y) (x + z) (3x + y) (2x + z) Then you need to find a way to get your constant 10 which you can either get from 1*10 or 10*1 or 5*2 or 2*5 leaves you with 8 possible solutions. Then you need to change the signs so you find the -7 x term. Sorry I can't explain it better I just do it without thinking about it so its really hard to explain now..... (6x + 5) (x - 2) Quote Link to comment Share on other sites More sharing options...
Simpson Posted September 10, 2012 Report Share Posted September 10, 2012 (edited) Which means x = -5/6 or 2 Since: (6x + 5) (x -2) = 0 means either: 6x + 5 = 0 or x -2 = 0 and rearrangeTo plot you know its a U shape because its an x^2 graph. Which crosses the x axis at -5/6 and +2. If x = 0 y = -10 so thats the y intercept, then I think you'll just be expected to know them and draw the rough shape. Edited September 10, 2012 by Simpson Quote Link to comment Share on other sites More sharing options...
LukasMcNeal Posted September 10, 2012 Author Report Share Posted September 10, 2012 Major confused! Ill just ask for some help but thats for trying help me guys Quote Link to comment Share on other sites More sharing options...
Simpson Posted September 10, 2012 Report Share Posted September 10, 2012 Sorry its real shit trying to give help over the internet, Rainbirds better at it than me. You at SEEIVC now? I'm at the bottom of bread and cheese and will probably be in for the next couple of days, so if you need any help just pop over dude Quote Link to comment Share on other sites More sharing options...
LukasMcNeal Posted September 10, 2012 Author Report Share Posted September 10, 2012 Cheers dude, but im at SEC in southend! I think I just need to be walked through it, going by my class mates they are pretty phased too so im sure our teacher will help us! Quote Link to comment Share on other sites More sharing options...
Simpson Posted September 10, 2012 Report Share Posted September 10, 2012 Ok man thats fine, I'm ill at the moment so if I get super bored and can think of a way to knock up a lil vid I will Quote Link to comment Share on other sites More sharing options...
Revolver Posted September 10, 2012 Report Share Posted September 10, 2012 It's not square root of 10, is it...? :/ Quote Link to comment Share on other sites More sharing options...
LukasMcNeal Posted September 10, 2012 Author Report Share Posted September 10, 2012 Thanks gonna talk to my tutor tommorow, I understand the factorisation bit almost now! Quote Link to comment Share on other sites More sharing options...
manuel Posted September 11, 2012 Report Share Posted September 11, 2012 then I think you'll just be expected to know them and draw the rough shape. Or for the marks, bung in some values for x and plot the graph ? For all the marks 1) plot a graph and see where it crosses the x-axis 2) factorise the equation ala Simps 3) use the formula x= (-b+/-sqrt(b^2 - 4ac))/2a, when the equation is in the form ax^2 + bx +c Quote Link to comment Share on other sites More sharing options...
Simpson Posted September 11, 2012 Report Share Posted September 11, 2012 Or for the marks, bung in some values for x and plot the graph ? Well I was always very lazy, if you have the 3 points and you know the "U" is going to be symmetrical then you can make an educated enough guess. I think my laziness is because on the AQA A-level board you only needed to label axis, make sure you found all intercepts and draw the right shape. Don't think we were even given graph paper! haha I'd always factorise then plot, but I guess personal preference. Back to the OP the main problem is in your question "6x^2 - 7x - 10 = 0" surely its ment to be 6x^2-7x-10= y? (haven't done this shit in ages) the Y-Axis is essentially x=0 and the X-Axis is essentially x=0. So youv'e missed a step - to find where it intercepts the y axis you make x=0 and to find the x intercept you make y=0. Yea I forgot the name of the formula last night, completing the square isn't it? Don't forget for your problem you have to divide everything by 6 intitially to make a single x^2 term and then just times by 6 at the end. Quote Link to comment Share on other sites More sharing options...
manuel Posted September 11, 2012 Report Share Posted September 11, 2012 I guess the question asked to solve it by graphing, so if you only plotted three points and two of them magically happened to be the solutions you may not get the marks! I would agree though - I would do the factorisation or equation method first to help you with drawing the graph. Knowing the answer before you begin is always great. For my gcse's I programmed my calculator to solve quadratics... I also had Newton raphson in there too although I don't think cubes are in there? Quote Link to comment Share on other sites More sharing options...
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