document.write( "Question 1209168: Find all ordered pairs (x,y) of real numbers such that x + y = 10 and x^2 + y^2 = 62 + 2xy.\r
\n" ); document.write( "\n" ); document.write( "For example, to enter the solutions (2,4) and (-3,9), you would enter \"(2,4),(-3,9)\" (without the quotation marks).
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Algebra.Com's Answer #847749 by greenestamps(13200)\"\" \"About 
You can put this solution on YOUR website!


\n" ); document.write( "\"x%2By=10\"
\n" ); document.write( "\"x%5E2%2By%5E2=62%2B2xy\"

\n" ); document.write( "Whenever the given equations have terms of \"x%5E2\", \"y%5E2\", and \"2xy\", one thing you want to look at is using one of these:

\n" ); document.write( "\"%28x%2By%29%5E2=x%5E2%2B2xy%2By%5E2\"
\n" ); document.write( "\"%28x-y%29%5E2=x%5E2-2xy%2By%5E2\"

\n" ); document.write( "For this problem....

\n" ); document.write( "\"x%5E2%2By%5E2=62%2B2xy\"
\n" ); document.write( "\"x%5E2-2xy%2By%5E2=62\"
\n" ); document.write( "\"%28x-y%29%5E2=62\"

\n" ); document.write( "Solve the first given equation for y in terms of x and substitute in this last equation.

\n" ); document.write( "\"y=10-x\"
\n" ); document.write( "\"x-y=x-%2810-x%29=x-10%2Bx=2x-10\"
\n" ); document.write( "\"%28x-y%29%5E2=%282x-10%29%5E2=62\"
\n" ); document.write( "\"4x%5E2-40x%2B100=62\"
\n" ); document.write( "\"4x%5E2-40x%2B38=0\"

\n" ); document.write( "That quadratic does not factor, so use the quadratic formula to find

\n" ); document.write( "\"x=%2840%2Bsqrt%28992%29%29%2F8\" and \"x=%2840-sqrt%28992%29%29%2F8\"

\n" ); document.write( "Partially simplified, those roots are

\n" ); document.write( "\"5%2Bsqrt%28992%29%2F8\" and \"5-sqrt%28992%29%2F8\"

\n" ); document.write( "The given equations are symmetrical in x and y, so the two solutions are that x and y are equal to, in either order, \"5%2Bsqrt%28992%29%2F8\" and \"5-sqrt%28992%29%2F8\"

\n" ); document.write( "Those numbers, confirmed by graphing the system of equations using desmos.com, are approximately 8.937 and 1.063.

\n" ); document.write( "ANSWERS (approximately): (8.937,1.603) and (1.063,8.937)

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