Algebra Pre-Algebra and Basic Algebra Math Forum

 June 5th, 2014, 08:08 AM #1 Newbie   Joined: Jun 2014 From: rhsfhb Posts: 24 Thanks: 0 help me solve this system of equations Here it is: x^2+3xy-8x^2 equals 20 x^2-y^2 equals 15 June 5th, 2014, 08:59 AM #2 Senior Member   Joined: Nov 2013 From: Baku Posts: 502 Thanks: 56 Math Focus: Geometry I assume it is $\displaystyle x^2+3xy-8y^2 = 20 \\ x^2-y^2 = 15$ Solution is intersection of two hyperbolas. $\displaystyle 8y^2 = 8x^2 - 120 \Rightarrow x^2 + 3xy - 8x^2 + 120 = 20 \Rightarrow y = \frac{7x^2 - 100}{3x} \Rightarrow x^2 - ( \frac{7x^2 - 100}{3x} )^2 = 15 \Rightarrow \\ \\ 9x^4 - 49x^4 + 1400x^2 - 10000 = 135x^2 \Rightarrow -40x^4 +1265x^2 - 10000 = 0 \Rightarrow x_{1,2} = \pm 4, \; \& \; x_{3,4} = \pm 2.5 \sqrt{2.5}$ Thanks from wannabemathlete June 5th, 2014, 10:05 PM #3 Newbie   Joined: Jun 2014 From: rhsfhb Posts: 24 Thanks: 0 Thanks a lot. I didnt noticed its actually that easy, thanks again for explanation  Tags equations, solve, system Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post roberthun Algebra 3 January 30th, 2013 05:52 AM Bucephalus Linear Algebra 2 January 29th, 2012 12:44 AM gopackers2011 Linear Algebra 1 October 13th, 2011 07:14 AM abotaha Calculus 2 August 3rd, 2010 10:43 AM Axle12693 Algebra 2 January 22nd, 2010 08:41 PM

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