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shayne80 · May 15, 2012, 01:55 PM

3x y=15 4x-3y=7

physic · May 26, 2012, 03:05 PM

$3x y=15$
$4x-3y=7$
$xy=\frac {15}{3}$
$xy=5$
$x=\frac {7+3y}{4}$
$\frac {7+3y}{4}y=5$
$\frac {3y^2){4}+\frac {7y}{4}-5=0$
$a=\frac {3}{4}$
$b=\frac {7}{4}$
$c=-5$
$y=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$

physic · May 26, 2012, 03:10 PM

Originally Posted by physic

$3x y=15$
$4x-3y=7$
$xy=\frac {15}{3}$
$xy=5$
$x=\frac {7+3y}{4}$
$\frac {7+3y}{4}y=5$
$\frac {3}{4}y^2+ {\frac {7}{4}y-5=0$
$a=\frac {3}{4}$
$b=\frac {7}{4}$
$c=-5$
$y=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$

$\frac {3}{4}y^2+ {\frac {7}{4}y-5=0$