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August 27th, 2014, 05:02 PM  #1 
Newbie Joined: Aug 2014 From: England Posts: 14 Thanks: 0 Math Focus: Calculus  Simultaneous Equations...
Hi, I was wondering if somebody could help me with this question please! Show that the elimination of X from the simultaneous equations: x2y = 1 3xyy^2 = 8 Produces the equation: 5y^2+3y8 = 0 Solve this quadratic equation and hence find the pairs of (x,y) for which the simultaneous equations are satisfied. Now the second part I can do easily, but eliminating X to produce the given equation is seeming to be rather difficult. Thank you! 
August 27th, 2014, 06:43 PM  #2 
Newbie Joined: Aug 2014 From: England Posts: 14 Thanks: 0 Math Focus: Calculus 
Never mind I got it! It was actually quite simple haha. In case anybody is wondering... X  2y = 1, so... X = 2y + 1 3y(2y+1)y^2 = 8 6y^2+3yy^2 =8 5y^2+3y=8 5y^2+3y8 = 0 
August 28th, 2014, 02:55 AM  #3 
Senior Member Joined: Apr 2014 From: Glasgow Posts: 2,156 Thanks: 731 Math Focus: Physics, mathematical modelling, numerical and computational solutions 
Well done! That method's called the substitution method, which is a nice method. The substitution method is also nice if you're given three equations and three unknowns (although your teacher may be a bit cruel to give you those kind of questions now!)


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