Problem my sister needs help with that I can't solve..

[squance]

Find the lengths that are cut off the x and y axes by the circle x^2 + y^2 - 2x -4y = 20

She has this as her working out so far...

x^2 - 2x + y^2 - 4y = 20
(x^2 - 2x + 1) - 1 + (y^2 - 4y + 4) - 4 = 20
(x-1)^2 + (y-2)^2 = 25

Centre = (1,2)
Radius = 5

The answer is 2 root 21 for x -axis and 4 root 6 for y- axis

my sister would appreciate the help

[cara.mel]

No need to have rearranged it like that

You are finding the lengths of the red and blue line in here: (this is not drawn to scale at all)


=> Find both places it intersects the x axis and subtract one from the other, same for y axis.
Eg for the x one, y=0 so you are solving x^2-2x=20

[squance]

Thanks...I'll show this to my sister when she gets home from tutoring