mydiamond Posted December 7, 2014 Report Share Posted December 7, 2014 I'm sorry to destroy the leisurely Holiday theme, but if you're good at Algebra please do lend a hand I can't find my notes on this one particular material and I have no clue what am I doing! They're due tomorrow EDIT: apparently variable 'i' isn't accepted in the final answer. I've tinkered around with these two questions since yesterday and I'm going crazy Quote Link to comment Share on other sites More sharing options...
Mazz Posted December 7, 2014 Report Share Posted December 7, 2014 Liv, sorry. I am good at algebra, but this goes beyond my knowledge base. Huskies in the Heartland Quote Link to comment Share on other sites More sharing options...
mydiamond Posted December 7, 2014 Author Report Share Posted December 7, 2014 Aw it's alright Dave thanks for trying x Quote Link to comment Share on other sites More sharing options...
robke Posted December 7, 2014 Report Share Posted December 7, 2014 Looks and is way above my paygrade... sorry Liv.. Quote Link to comment Share on other sites More sharing options...
Emma Posted December 7, 2014 Report Share Posted December 7, 2014 Oh god, that makes my head spin just looking at it. Sorry Liv but I won't be any help. Hope you manage to get some help. [emoji1] Quote Link to comment Share on other sites More sharing options...
qweasd Posted December 7, 2014 Report Share Posted December 7, 2014 -5 and 3i are solutions means that (x + 5) and (x - 3i) are factors of the equation. f(x) = (x + 5)(x - 3i)(ax + f(-1) = 120 = (-1 + 5)(-1 - 3i)(-a + Multiple this out and you should be able to work out the values for a and b For the next problem, you will have two unknown factors of the equation so you will have two factors (ax + and (cx + d) to work out. Quote Link to comment Share on other sites More sharing options...
Mazz Posted December 7, 2014 Report Share Posted December 7, 2014 I just knew we had to have a math wizard here. Way to go Adam. Quote Link to comment Share on other sites More sharing options...
mydiamond Posted December 7, 2014 Author Report Share Posted December 7, 2014 -5 and 3i are solutions means that (x + 5) and (x - 3i) are factors of the equation. f(x) = (x + 5)(x - 3i)(ax + f(-1) = 120 = (-1 + 5)(-1 - 3i)(-a + Multiple this out and you should be able to work out the values for a and b For the next problem, you will have two unknown factors of the equation so you will have two factors (ax + and (cx + d) to work out. Thank you thank you thank you! I simply multiplied the (x+5) (x-3i) and forgot the last bit Quote Link to comment Share on other sites More sharing options...
robke Posted December 7, 2014 Report Share Posted December 7, 2014 simple LOL if you know how.... Quote Link to comment Share on other sites More sharing options...
Andy Posted December 7, 2014 Report Share Posted December 7, 2014 My brain hurts just looking at that !! Quote Link to comment Share on other sites More sharing options...
Mazz Posted December 7, 2014 Report Share Posted December 7, 2014 And here I thought this was just a Husky forum. Huskies in the Heartland Quote Link to comment Share on other sites More sharing options...
mydiamond Posted December 7, 2014 Author Report Share Posted December 7, 2014 Yep I gave up. I can't find an equation that makes sense for the life of me. Ended up working on Biology instead. *sigh* thanks for giving me a starting point though Adam xx Quote Link to comment Share on other sites More sharing options...
Elyse Posted December 7, 2014 Report Share Posted December 7, 2014 (edited) EDIT: Sorry, Olivia. I couldn't find the binder. Maybe I threw them out. Hey, Olivia....I might still my Calculus notes from last year. If it isn't too late, I can try to find the material on how to do it, and then scan you a copy. (I knew those Calculus notes would come in handy someday!) Edited December 7, 2014 by SolitaryHowl Quote Link to comment Share on other sites More sharing options...
qweasd Posted December 7, 2014 Report Share Posted December 7, 2014 I tried to do it using that method and realised there is an easier method. Consider f(x) = A x^3 + B x^2 + C x + D Work out f(3i). This equals 0, so the real and imaginary parts of the equation are both 0. This gives you 2 equations for A, B, C & D. Now work out f(-5) which also equals 0. This gives you another equation for A, B, C & D. Finally work out f(-1) which equals 120. This gives you a 4th equation for A, B, C & D. These 4 equations are sufficient to work out the values for A, B, C & D. You can then factor the equation knowing that (x + 5) and (x - 3i) are factors. I have worked this through so I can give you more info if required. Quote Link to comment Share on other sites More sharing options...
qweasd Posted December 7, 2014 Report Share Posted December 7, 2014 I've worked through the second question as well and it will work in the same way but you will have A, B, C, D & E. Also, when you come to factor the equation don't try using (x - 6i) and (x + 4i) as this is complicated. Instead, substitute y = x^2 and solve for y. Once you have values for y, then replace x in the equations and solve for x. This does sound a bit complicated but it will be easier once you have the equations (I'm trying not to give you the answer). There were also some big numbers (100s in the first question and 1000s in the second question). Quote Link to comment Share on other sites More sharing options...
qweasd Posted December 7, 2014 Report Share Posted December 7, 2014 I'm going to start a new topic with the solutions in case you get stuck. Hopefully you will work through the problems yourself before checking your answers. Quote Link to comment Share on other sites More sharing options...
sarahjng Posted December 7, 2014 Report Share Posted December 7, 2014 Even after reading the question, and all Adams answers, it still looks like Russian code for the Muppet song ! Quote Link to comment Share on other sites More sharing options...
Dan Posted December 7, 2014 Report Share Posted December 7, 2014 Geez now I feel right at home, this is why I kinda gave up on engineering Quote Link to comment Share on other sites More sharing options...
mydiamond Posted December 7, 2014 Author Report Share Posted December 7, 2014 Rant: I just WISH they don't include i anywhere in this equation *grumble grumble*. What annoys me most is that this is actually an easy question made difficult thanks to Mr. i @Elyse: Whoa I don't even speak Calculus thanks though! @Adam: Great idea I never thought you can set it up like that. Darn. I left my pencil case in my room at the fourth floor. Quote Link to comment Share on other sites More sharing options...
qweasd Posted December 8, 2014 Report Share Posted December 8, 2014 Even after reading the question, and all Adams answers, it still looks like Russian code for the Muppet song ! You will really like Quote Link to comment Share on other sites More sharing options...
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