Math Is Fun Forum

runlemmingsrun1

Guest

find an equation..

Please help me find the
1:Equation for a line that passes through the points (1,2) and (12,24).

2:  Equation for a circle with a radius of 9 and a midpoint of (3,3).

Thanks

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: find an equation..

For the first one, try Calculate the Straight Line Graph

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"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

mahmoudaljamel

Member

Registered: 2006-09-03

Posts: 18

Re: find an equation..

hi ,
for a line passing through (x1,y1) and (x2,y2) , use this equation :
m (slope) = (y2-y1)/(x2-x1)
y-y1 = m(x-x1)
in our case :
m= 24-2 / 12-1 = 22/11 = 2
y - 2 = 2 ( x- 1)
y - 2 = 2x-2
y = 2x

For the circle :
The equation used is the standard equation that has the form

(x - h)² + (y - k)² = r2
where h and k are the x- and y-coordinates of the center of the circle and r is the radius.
( x-3)[sup]2[/sup] + ( y-3)[sup]2[/sup] = 81

Last edited by MathsIsFun (2006-09-13 00:26:51)

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If you always do what you always did, you'll always get what you always got

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: find an equation..

Hi Mahmoud, and welcome to the forum. Nice work.

I took the liberty of *slightly* editing your post - to make the "2"s as exponents, first by using the little "2"s at the top of the forum (I did a copy and paste), and secondly by using the "sup" tag.

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"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

mahmoudaljamel

Member

Registered: 2006-09-03

Posts: 18

Re: find an equation..

thanks

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If you always do what you always did, you'll always get what you always got