document.write( "Question 565942: A plane flies 600 miles against a steady 40 mph headwind, and then returns to the same point, with the wind. If the entire trip takes takes 8 hours, what is the plane’s speed in still air? \n" ); document.write( "
Algebra.Com's Answer #366028 by mananth(16946)\"\" \"About 
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Plane speed x mph
\n" ); document.write( "wind speed 40 mph
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\n" ); document.write( "against wind x- 40 mph
\n" ); document.write( "with wind x+ 40 mph
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\n" ); document.write( "Distance= 600 miles
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\n" ); document.write( "Time against + time with = 8 hours
\n" ); document.write( "t=d/r \r
\n" ); document.write( "\n" ); document.write( "600/(x+40)+600/(x-40)= 8
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\n" ); document.write( "LCD = (x-40)(x+40)
\n" ); document.write( "600 *(x-40)+600(x+40)=8
\n" ); document.write( "600x-24000+600x+24000=8(x ^2-1600)
\n" ); document.write( "1200x= 8x ^2-12800
\n" ); document.write( "8x ^2-1200x-12800\r
\n" ); document.write( "\n" ); document.write( "8x^2+80x-1280x-12800=0
\n" ); document.write( "8x(x+10)-1280(x+10)=0\r
\n" ); document.write( "\n" ); document.write( "(x+10)(8x-1280)=0
\n" ); document.write( "8(x+10)(x-160)=0
\n" ); document.write( "x=160 which is positive\r
\n" ); document.write( "\n" ); document.write( "speed of plane = 160 mph
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