Standard Equation for Circles!!!!!! HELP "/

[yani]

i'm pretty good with finding the standard equation for circles, but this new unit my clas is working on requies me to "complete the square" and i'm totally confused!! any ideas??

 

[burakaltr]

i'm pretty good with finding the standard equation for circles, but this new unit my clas is working on requies me to "complete the square" and i'm totally confused!! any ideas??

Take

Ax**2 + B x + C=0

can re-write as

x**2+B x + (B/(2A))**2 x+ ( C-(B/(2A))**2 )=0


what is done is for completion of the square, one's got to add the square of the coeff divided by 2 and square it , when the coeff of x**2 is stripped of
A

We add an amount ( B/(2A))**2

or when we are A free

just in Ax**2 +Bx+C=0=x**2 +b x +c

taking

x**2 + b x + c

halve b ( coeff of x ) then square it

add the result to eqtn

subtract same amount from c , so that you have done no change

therefore

( x + (b/2) )**2 is attained for a complete square

now subtract this ((b/2)**2) from c

(x+(b/2))**2 + c - (b/2 ) **2

This is the final equality

 

[yani]

thanks!

i passed the test with a 82, so thanks for your input!!!