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Teachers and Students => Universities => Topic started by: SGVaibhav on January 11, 2010, 05:35:17 am

Title: 2 Simple Questions!
Post by: SGVaibhav on January 11, 2010, 05:35:17 am
1) Solve the following inequality :             
|x-2|>1

2) Find the equation of the circle that passes through (0,1) (2,0) (3,4)
Title: Re: 2 Simple Questions!
Post by: astarmathsandphysics on January 11, 2010, 08:39:59 am
When I get up
Title: Re: 2 Simple Questions!
Post by: SGVaibhav on January 11, 2010, 08:46:28 am
u wrote the reply in dreams or while sleeping (sleep writing / sleep posting?)
lool
Title: Re: 2 Simple Questions!
Post by: astarmathsandphysics on January 11, 2010, 08:50:27 am
Yes I was sleep posting
Title: Re: 2 Simple Questions!
Post by: astarmathsandphysics on January 11, 2010, 09:46:40 am
1) Solve the following inequality :             
|x-2|>1

2) Find the equation of the circle that passes through (0,1) (2,0) (3,4)

) Solve
x-2>1 and x-2<-1
x>3 or x<1
2)The equation of a circle is given by
x^2+y^2+ax+by=c
Sub each point in and solve the simultaneous equations
1+b+c=0(1)
4+2a+c=0(2)
25+3a+4b+c=0(3)
(2)-(1) 3+2a-b=0 (4)
(3)-(1)24+3a+3c=0 so 8+a+b=0 (5)
(4)+(5) 11+3a=0 so a=-3/11
then from (5)8-3/11+b=0 so b=-85/3
Then from (1) 1-85/3+c=0 so c=82 over 3
x^2+y^2-3x/11-85y/3+82/3=0

Title: Re: 2 Simple Questions!
Post by: SGVaibhav on January 11, 2010, 09:52:58 am
understood everything EXCEPT, what do u do after finding a, b and c in the 2nd question.
Title: Re: 2 Simple Questions!
Post by: astarmathsandphysics on January 11, 2010, 10:51:43 am
sub them into th e formula for the circle x^2+y^2+ax+by=c
Title: Re: 2 Simple Questions!
Post by: SGVaibhav on January 11, 2010, 03:28:46 pm
so how do we then get the center and radius, i forgot ???
Title: Re: 2 Simple Questions!
Post by: astarmathsandphysics on January 11, 2010, 03:50:06 pm
Complete the square. Will do it proper when I get home
Title: Re: 2 Simple Questions!
Post by: SGVaibhav on January 11, 2010, 04:39:28 pm
oh yeah, i found out something...

i got another method, it says Centre = (-A/2  , -B/2)    (i dont know if its right)
                                    and radius = Square root of ( (-a/2)^2  +   (-b/2)^2   - c))     [square root of   -a/2 square + -b/2 square - c]
Title: Re: 2 Simple Questions!
Post by: astarmathsandphysics on January 11, 2010, 08:06:12 pm
Yes that is true