wolfson Posted December 13, 2003 Share Posted December 13, 2003 Ok im going to have a go at holding a quiz........ Q: Factorise completely the expression: f(x) = 3x^2 + x^2 - 12X -4, and hence solve the equation f(x) = 0. Ok try and solve the question, and gl to you all.... Winners will be announced in 2 days. Link to comment Share on other sites More sharing options...
psi20 Posted April 9, 2004 Share Posted April 9, 2004 0=4x^2 - 12x - 4 0=4(x^2 - 3x - 1) 0=x^2-3x-1 (3+/-sqrt13)/2 Link to comment Share on other sites More sharing options...
Leison Posted July 17, 2004 Share Posted July 17, 2004 f(x)=3x^2+x^2-12x-4 =4x^2-12x-4 =4(x^2-3x-1) f(x)=0 {given} so we can write, 4(x^2-3x-1)=0 (x^2-3x-1) =0 {4<>0} using formula, we have x=3.3 or -.3 Link to comment Share on other sites More sharing options...
Dave Posted July 18, 2004 Share Posted July 18, 2004 Since you have f(x) defined to be the function 3x2 + x2 - 12X -4, can we assume x = X? Link to comment Share on other sites More sharing options...
wolfson Posted July 18, 2004 Author Share Posted July 18, 2004 lol yes Link to comment Share on other sites More sharing options...
Dave Posted July 18, 2004 Share Posted July 18, 2004 In that case I won't bother doing it then Link to comment Share on other sites More sharing options...
Primarygun Posted July 20, 2004 Share Posted July 20, 2004 Need I wait for another week to post question ? Link to comment Share on other sites More sharing options...
Dave Posted July 22, 2004 Share Posted July 22, 2004 Say what now? You can post questions anytime you like. Link to comment Share on other sites More sharing options...
Guest mathfreak Posted September 1, 2004 Share Posted September 1, 2004 Test post. This is my first visit here. cheers. Link to comment Share on other sites More sharing options...
Severian Posted September 3, 2004 Share Posted September 3, 2004 Did you perhaps mean: f(x) = 3 x3 + x2 - 12 x - 4 ? If so, f(x) = (x2-4)(3x+1) = (x-2)(x+2)(3x+1) f(x) = 0 => x = -2, +2, or -1/3 Link to comment Share on other sites More sharing options...
paganinio Posted September 4, 2004 Share Posted September 4, 2004 Reasonable Cheers, Severian Just like a question which has been given the 'official answer',but in fact there's more to think about. There're 2 evidences that Severian is right. 1,The original question is weird.'f(x) = 3x^2 + x^2 - 12X -4'=0 2,The original answer is also a little weird.'(3+/-sqrt13)/2' Link to comment Share on other sites More sharing options...
Guest tenlientl Posted September 22, 2004 Share Posted September 22, 2004 Whoa...... This is veyr shocking. I don't get all these f(x) and stuff. I'm in grade 11. Is it normal for a grade 11 to not know this? Link to comment Share on other sites More sharing options...
jordan Posted September 23, 2004 Share Posted September 23, 2004 Normal is rather tough to define. I've know about it since probably 9th grade, but there are others in 12th with me who still don't know. The f(x) is probably what you normaly call y. As in y=2x is the same as f(x)=2x. f(x) basicaly says that for a given value of x, what is the result of the function. Link to comment Share on other sites More sharing options...
Dave Posted September 23, 2004 Share Posted September 23, 2004 In more depth, f is a function which takes a variable (or perhaps more than one variable in some cases), and by performing an operation on it converts it to some other number. Link to comment Share on other sites More sharing options...
dash00 Posted May 23, 2005 Share Posted May 23, 2005 Whoa...... This is veyr shocking. I don't get all these f(x) and stuff. I'm in grade 11. Is it normal for a grade 11 to not know this? depends what level of maths you do, i was confused by using f(x) as opposed to y= when we were first taught to use it, which was at the begining of year 11. Link to comment Share on other sites More sharing options...
BigMoosie Posted May 31, 2005 Share Posted May 31, 2005 It doesnt have to always be f, it can be any other variable or even word such as the well know trig functions. You recognise the notation of sin(30) = 1/2, as you see, one or more numbers in, but always only one number out. Link to comment Share on other sites More sharing options...
TheGeek Posted May 31, 2005 Share Posted May 31, 2005 f(x) = 3x^2 + x^2 -12x -4 f(x) = 4x^2 - 12x - 4 f(x) = 4(x^2 - 3x 1) using the quadratic formula you could figure out that f(x) is either 3.309 or -.309 Link to comment Share on other sites More sharing options...
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