1. ## Co-ords intersection

How do i find the co ordiantes of the points of intersection of the circle x^2+y^2=25 and the line y=3x, and leave this in surd form. Thanks

2. Originally Posted by Chez_
How do i find the co ordiantes of the points of intersection of the circle x^2+y^2=25 and the line y=3x, and leave this in surd form. Thanks
$x^2 + y^2 = 25$

$y = 3x$

$x^2 + (3x)^2 = 25$

$x^2 + 9x^2 = 25$

$10x^2 = 25$

$x^2 = 2,5$

$x = \pm \sqrt{2,5}$

Set those values into the original equation to find the corresponding y-values.

3. Originally Posted by Chez_
How do i find the co ordiantes of the points of intersection of the circle x^2+y^2=25 and the line y=3x, and leave this in surd form. Thanks
In general, to find an intersection of two functions (the circle really isn't a function, but we make it into one), you set them equal to each other.