Homework Help Forum: Pre Calc still confused

Posted by Muffy on Saturday, October 24, 2009 at 5:00pm.

Solve: (x+5/x)+(6/x-4)=(-7/x^2-4x) I multiplied the entire function by x and x-4 and after doing that I got down to the quadratic equation x^2+7x-13=0 I did the quadratic and got x=1.525 and -8.525 I feel like I made a mistake because when I plug in both of those answers for x separately, it never works out. Not sure if I made an error in calculating or in plugging in, or if there is no solution. Thanks.

• Pre Calc still confused - bobpursley, Saturday, October 24, 2009 at 6:17pm

  (x+5)(x-4)+ 6x=-7 x^2+x-20+6x=-7 x^2+7x-13=0 x= (-7 +-sqrt (49+52))/2=(-7+-10.04)/2 x=-17/2, 3/2 your answers

  
  

• Pre Calc one more thing - Muffy, Saturday, October 24, 2009 at 6:28pm

  When I plug them in they don't work. am I plugging them in wrong or is it no solution?

  
  

• Pre Calc still confused - jim, Saturday, October 24, 2009 at 6:32pm

  Are the brackets right? I've tried (x+5/x)+(6/x-4)=(-7/x^2-4x), and (x+5)/x + 6/(x-4)=-7/(x^2-4x) and a couple of other permutations without achieving enlightenment.

  
  

• Pre Calc still confused - jim, Saturday, October 24, 2009 at 6:53pm

  OK. If it's (x+5)/x + 6/(x-4)=-7/(x^2-4x) then I agree with bobpursley's answer but the numerical answers aren't exactly -17/2 and 3/2; they're (-7+-sqrt(101))/2. If you plug 3/2 in, it'll be close but not zero. 6.5/1.5 + 6/(1.5-4)+7/(1.5^2-4*1.5)

  
  

• Pre Calc still confused - jim, Saturday, October 24, 2009 at 6:55pm

  Oops. Left off the last equals: 6.5/1.5 + 6/(1.5-4)+7/(1.5^2-4*1.5) = 0.066666...

  
  

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