Algebra Pre-Algebra and Basic Algebra Math Forum

 January 30th, 2019, 07:43 AM #1 Member   Joined: Oct 2012 Posts: 78 Thanks: 0 Find If x(y+z)=39, y(z+x)=60, z(y+x)=63 Find x^2+y^2+z^2 January 30th, 2019, 09:14 AM #2 Senior Member   Joined: Dec 2015 From: somewhere Posts: 551 Thanks: 83 eq(1)+eq(2)-eq(3) gives xy=12 . Same thing is for yz and xz . Thanks from fahad nasir and topsquark January 30th, 2019, 09:15 AM #3 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1038 xy + xz + 00 = 39 xy + 00 + yz = 60 00 + xz + yz = 63 3 equations, 3 unknowns...so solve for each unknown. Suggest you use elimination process... Thanks from fahad nasir, topsquark and JeffM1 January 30th, 2019, 09:29 AM #4 Global Moderator   Joined: Dec 2006 Posts: 20,835 Thanks: 2162 The given equations are linear in xy, xz and yz, with solution (xy, xz, yz) = (18, 21, 9). Hence x² = (xy)(xz)/(yz) = 9, and, similarly, y² = 36 and z² = 49, so x² + y² + z² = 94. Thanks from fahad nasir, topsquark and JeffM1 Tags find 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 harryp Algebra 2 September 8th, 2015 08:11 PM mared Trigonometry 3 July 2nd, 2014 08:09 AM kingkos Algebra 5 November 24th, 2012 11:40 PM kevinman Algebra 8 March 8th, 2012 05:53 AM

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