Kieran Morrison Posted March 29, 2011 Report Share Posted March 29, 2011 How do you subtract equations? something like this: 2-5x = 63 Is it just the same as a plus sign and you do it the exact same or is it different (explain if you can) And in the last test i got this : if x = 6 and y= -3 what is xy2. I didnt know how to do it, can someone explain? got another test thing and this one really bugged me Cheers Quote Link to comment Share on other sites More sharing options...
Dwarf Shortage Posted March 29, 2011 Report Share Posted March 29, 2011 'if x = 6 and y= -3 what is xy2' You alway do squares first, so x(y2) becomes 6 x (-32), and when you square a minus number it just becomes positive, so -3 squared is 9. 6 x 9 = 54. xy2 = 54 Quote Link to comment Share on other sites More sharing options...
Kieran Morrison Posted March 29, 2011 Author Report Share Posted March 29, 2011 'if x = 6 and y= -3 what is xy2' You alway do squares first, so x( y2) becomes 6 x (-32), and when you square a minus number it just becomes positive, so -3 squared is 9. 6 x 9 = 54. xy2 = 54 So how would you write the equation out? Quote Link to comment Share on other sites More sharing options...
Jon Alty Posted March 29, 2011 Report Share Posted March 29, 2011 (edited) 'if x = 6 and y= -3 what is xy2' You alway do squares first, so x(y2) becomes 6 x (-32), and when you square a minus number it just becomes positive, so -3 squared is 9. 6 x 9 = 54. xy2 = 54 This ^. If there are no signs between letters or brackets, then you multiply them ytogether. Sometimes they also use dots to mean multiply, for exampls 8/6.9/7 =8/6*9/7. 2) 2-5x = 63 Here your just trying to find x, so you need to isollate x and then solve. -> minus 2 from each side = -5x=61 -> swap signs to leave x alone = 5x=-61 -> Divide each side by 5 to leave just x = x=-12.2 Edited March 29, 2011 by Jon Alty Quote Link to comment Share on other sites More sharing options...
Aidan97 Posted March 29, 2011 Report Share Posted March 29, 2011 Am I the only stupid one on trials forum because I hardly get this. Quote Link to comment Share on other sites More sharing options...
Kieran Morrison Posted March 29, 2011 Author Report Share Posted March 29, 2011 This ^. If there are no signs between letters or brackets, then you multiply them ytogether. Sometimes they also use dots to mean multiply, for exampls 8/6.9/7 =8/6*9/7. 2) 2-5x = 63 Here your just trying to find x, so you need to isollate x and then solve. -> minus 2 from each side = -5x=61 -> swap signs to leave x alone = 5x=-61 -> Divide each side by 5 to leave just x = x=-12.2 cheers mate, helped a lot! See if it was 5x-2=63 would you just do it like you woulf when there's a + instead of the -? Quote Link to comment Share on other sites More sharing options...
Jon Alty Posted March 29, 2011 Report Share Posted March 29, 2011 (edited) cheers mate, helped a lot! See if it was 5x-2=63 would you just do it like you woulf when there's a + instead of the -? Your just trying to find what x is, so to do that, get you need to get x=???. To do that, do stuff to both sides of the equation, that will leave you with x=???. So for that one, Add 2 to both sides; 5x=65 Divide both sides by 5; x=13 Remember, what you do to one side you MUST do to the other side. Edited March 29, 2011 by Jon Alty Quote Link to comment Share on other sites More sharing options...
Simpson Posted March 29, 2011 Report Share Posted March 29, 2011 (edited) What people struggle to understand, is that letters just represent numbers, same for pretty much any symbols, later they will probably use greek symbols and stuff to throw you off but its all the same stuff. At that level, any letter represents any real, constant number. So instead of writing 6 x 2 = 12 you can write A x B = C when A= 6, B= 2 and C= 12 so don't get confussed by it all. If you have an unknown variable isolate it and then work it out. i.e. 2 + 2A = 18 (first of all move the 2 across - remember you can put anything from 1 side of an equals sign to the other if you switch the sign) 2A = 16 (then you can divide both sides by 2 so that) A=8 SIMPLES Edited March 30, 2011 by Simpson Quote Link to comment Share on other sites More sharing options...
Krisboats Posted March 29, 2011 Report Share Posted March 29, 2011 What people struggle to understand, is that numbers just represent numbers I'd imagine most people get that to be fair 1 Quote Link to comment Share on other sites More sharing options...
Simpson Posted March 29, 2011 Report Share Posted March 29, 2011 How do you subtract equations? something like this: 2-5x = 63 I'd imagine most people get that to be fair Really? lol Looks pretty basic to me! Quote Link to comment Share on other sites More sharing options...
Krisboats Posted March 29, 2011 Report Share Posted March 29, 2011 Really? lol Looks pretty basic to me! Yeah, you said numbers represent numbers. 1=1 2=2 3=3 etc Quote Link to comment Share on other sites More sharing options...
Simpson Posted March 30, 2011 Report Share Posted March 30, 2011 (edited) Yeah, you said numbers represent numbers. 1=1 2=2 3=3 etc OH..... DOH Ill justify my mistake, because ive spent the whole fricking day revising stats, for my test on Thursday and Im very tired and pissed off with maths! haha yea maths, great degree choice dickhead. Edited March 30, 2011 by Simpson Quote Link to comment Share on other sites More sharing options...
Kieran Morrison Posted March 30, 2011 Author Report Share Posted March 30, 2011 Add 2 to both sides; 5x=65 if you add 2 to both sides, you get 5x - 4 = 65? so you cant divide until the 4 is gone? Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 30, 2011 Report Share Posted March 30, 2011 Add 2 to both sides; 5x=65 if you add 2 to both sides, you get 5x - 4 = 65? so you cant divide until the 4 is gone? Think about it... ignore the x's for now. -2 + 2 = 0. It doesn't equal -4 does it? The negative sign before the two is attached to the term in the equation so you are adding 2 to minus 2. Quote Link to comment Share on other sites More sharing options...
JT! Posted March 30, 2011 Report Share Posted March 30, 2011 if you add 2 to both sides, you get 5x - 4 = 65? so you cant divide until the 4 is gone? Lets brake it down more. 5x-2=63 If you plus two to both sides you get. 5x-2+2=63+2 on one side, you have 63+2 which is 65, so now we have. 5x-2+2=65 -2+2=0 (If you have -2 pounds in your back account and you go put 2 pounds in it, you'll have a balance of 0) so you now have... 5x+0=65 Obviously the +0 can be ignored.... 5x=65 Then you divide both sides by 5. x=13. Quote Link to comment Share on other sites More sharing options...
King C Posted March 30, 2011 Report Share Posted March 30, 2011 Think about it... ignore the x's for now. -2 + 2 = 0. It doesn't equal -4 does it? The negative sign before the two is attached to the term in the equation so you are adding 2 to minus 2. Your clearly not helping with your avatar are you? Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 30, 2011 Report Share Posted March 30, 2011 Your clearly not helping with your avatar are you? Quote Link to comment Share on other sites More sharing options...
Kieran Morrison Posted March 30, 2011 Author Report Share Posted March 30, 2011 Think about it... ignore the x's for now. -2 + 2 = 0. It doesn't equal -4 does it? The negative sign before the two is attached to the term in the equation so you are adding 2 to minus 2. but its not a negative number, its subtracting it. Anyway i looked in maths and i know what to do, thanks guys Quote Link to comment Share on other sites More sharing options...
JD™ Posted March 30, 2011 Report Share Posted March 30, 2011 but its not a negative number, its subtracting it. Anyway i looked in maths and i know what to do, thanks guys It is a negative number in that sense, because it's the same as writing it as -2+5x=63 What signifies a negative number? And what's in front of the 2? Hmm... coincedence? Good thing you've got it, but there's a lot to learn! Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 30, 2011 Report Share Posted March 30, 2011 but its not a negative number, its subtracting it. Anyway i looked in maths and i know what to do, thanks guys In equations, the terms (either a number, letter or combination of both) are given a sign (either positive or negative) which is initially 'attached to the term'. In the above equation in JD's post there are three terms: -2, +5x and +63. Addition and subtraction don't really come into it until you start manipulating the equation in order to solve it. Edit: Subtraction is an operation. Something being negative is different and you need to identify the difference between the two. Quote Link to comment Share on other sites More sharing options...
Kieran Morrison Posted March 30, 2011 Author Report Share Posted March 30, 2011 (edited) So, would i be right in saying that if there is 2 minus's in an equation, it means you add them, the same with 2 + signs, and if there is a minus and a plus you minus them? and you treat the number with the - infront of it like a negative? So if there is 9x+21=5x-4, you would minus 5x from each side, then minus 4 of each giving you 4x = 17 then divide them both by 4 giving you the answer- X = 14.25? If i did this wrong, please point out where i went wrong. Cheers!! Edit: noticed the mistake myself, fixed Edited March 30, 2011 by Kieran Morrison Quote Link to comment Share on other sites More sharing options...
JD™ Posted March 30, 2011 Report Share Posted March 30, 2011 So, would i be right in saying that if there is 2 minus's in an equation, it means you add them, the same with 2 + signs, and if there is a minus and a plus you minus them? and you treat the number with the - infront of it like a negative? So if there is 9x+21=5x-4, you would minus 5x from each side, then minus 4 of each giving you 4x = 17 then divide them both by 4 giving you the answer- X = 14.25? If i did this wrong, please point out where i went wrong. Cheers!! Edit: noticed the mistake myself, fixed No, minus 5x from each side to give 4x+21=-4 Then take 21 from each side to get x on it's own: 4x = -25 Then divide by 4 to get a single x: x = -(25/4) (that's -6.25) Quote Link to comment Share on other sites More sharing options...
Kieran Morrison Posted March 30, 2011 Author Report Share Posted March 30, 2011 No, minus 5x from each side to give 4x+21=-4 Then take 21 from each side to get x on it's own: 4x = -25 Then divide by 4 to get a single x: x = -(25/4) (that's -6.25) Sounds complicated, i put up a hard example we havent even been tought about that yet Quote Link to comment Share on other sites More sharing options...
JD™ Posted March 30, 2011 Report Share Posted March 30, 2011 Nah it's no more complicated that your last stuff, I just take that last line as: The divide by 4 to get a single x: x = -6.25 I was just encouraging good practise with fractions that you'll be taught at another time, but shouldn't have confused the issue for now! Does that make sense? Quote Link to comment Share on other sites More sharing options...
Kieran Morrison Posted March 30, 2011 Author Report Share Posted March 30, 2011 Nah it's no more complicated that your last stuff, I just take that last line as: The divide by 4 to get a single x: x = -6.25 I was just encouraging good practise with fractions that you'll be taught at another time, but shouldn't have confused the issue for now! Does that make sense? Yeah, was a stupid mistake i made putting the 17 on the wrong side. The last test i had i forgot to take away one of the numbers, and now i wont make the mistake you pointed out, Quote Link to comment Share on other sites More sharing options...
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