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Mathematics 7 Online
OpenStudy (sepeario):

Could I please have some assistance with this question? http://i.imgur.com/rbg1uxR.jpg

OpenStudy (ahsome):

Thats actually a very interesting equaiton.

OpenStudy (sepeario):

Yes it is, I'm learning quadratic equations right now, and this was one of the harder problems.

OpenStudy (ahsome):

Could we move the A, B and C values (not squared) to the RHS. Then take the square as the common value?

hartnn (hartnn):

not sure how this would help but \(\Large (a+2)^2 + (b-6)^2 + (c+5)^2 = 0\) because 65 can be split as 4 +36+ 25

OpenStudy (sepeario):

Actually that's a very good idea!

OpenStudy (sepeario):

but i don't know that helps to solve the equation...

OpenStudy (ahsome):

\[\large{a^2+b^2+c^2+4a-12b+10c=-65}\] \[\large{a^2+b^2+c^2=-65-4a+12b-10c}\] \[\large{(a+b+c)^2=-65-4a+12b-10c}\]Then, go to 2015, maybe?

OpenStudy (sepeario):

haha and how do i increase it to that power?

OpenStudy (perl):

go by even powers , first , i would try

OpenStudy (ahsome):

(BTW, is what I did even help?)

OpenStudy (sepeario):

yeah it helps a lot actually

hartnn (hartnn):

\(a^2+b^2+c^2 \ne (a+b+c)^2\)

OpenStudy (ahsome):

Oh, damnit :(

OpenStudy (ahsome):

Is there anyway we could take the square as common?

OpenStudy (sepeario):

what does that mean? @Ahsome

OpenStudy (ahsome):

To remove the square from the LHS.

OpenStudy (perl):

$$ \large{ (a+b+c)^2=-65-4a+12b-10c\\ \\ \therefore\\ (a+b+c)^4\\ =(-65-4a+12b-10c)^2\\ =(4a-12b+10c+65)^2 \\ \therefore\\ (a+b+c)^4=(4a-12b+10c+65)^2 \\ \therefore \\ (a+b+c)^8=(4a-12b+10c+65)^4 \\ etc. }\\ $$

OpenStudy (sepeario):

but a^2 + b^2 + c^3 doesn't equal the (a+b+c)^2

OpenStudy (ahsome):

Yeah. We established that after @perl started to solve :(

OpenStudy (sepeario):

what the guy said at the start was right, i found the solution. 65 can be expressed as 4, 25 and 36.

OpenStudy (sepeario):

you then divide them into three trinomials.

hartnn (hartnn):

you got it using my hint? :O please enlighten us too :)

hartnn (hartnn):

@perl \(a^2+b^2+c^2 \ne (a+b+c)^2\)

OpenStudy (perl):

i dont think i claimed that unless i made a mistake somewhere

hartnn (hartnn):

you started with (a+b+c)^2 itself... instead of starting with initial equation...

OpenStudy (perl):

oh Ahsome claimed it, and i might have worked off that

OpenStudy (perl):

*egad*

OpenStudy (ahsome):

Yup, whoops, sorry @perl

OpenStudy (perl):

@Sepeario do you have the answer, i'm not sure if you have a solution or not

OpenStudy (sepeario):

Don't worry, I figured it out, but thanks for the help guys!

OpenStudy (ahsome):

How????

OpenStudy (perl):

yes please show

OpenStudy (sepeario):

hartnn (hartnn):

oh wow!

hartnn (hartnn):

*facepalm* :P

OpenStudy (perl):

yes that looks too easy :)

OpenStudy (perl):

but hartnn did the hard work. the tricky part was finding a suitable factoring of the original expression

hartnn (hartnn):

if a^2+b^2+c^2 = 0 then a = b= c = 0 is a must :D

OpenStudy (sepeario):

quick question how do we find the values of a b and c?

OpenStudy (perl):

solve that simultaneously

hartnn (hartnn):

you did find it \(\Large (a+2)^2 + (b-6)^2 + (c+5)^2 = 0 \\ \Large a+2 = 0; b-6 = 0 , c+5 = 0 \\ \Large a= -2, b = 6, c = -5\)

OpenStudy (sepeario):

oh right lol

OpenStudy (perl):

hartn, so you basically completed the square

OpenStudy (perl):

for the sphere

OpenStudy (perl):

actually its a degenerate sphere (a single point)

hartnn (hartnn):

thats right

OpenStudy (perl):

treating a,b,c as variables

OpenStudy (perl):

nice

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