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Mathematics 17 Online
OpenStudy (anonymous):

Help

OpenStudy (anonymous):

Simultaneous equations

OpenStudy (anonymous):

\[\huge \sqrt{a}+b=7\] \[\huge \sqrt{b}+a=11\]

OpenStudy (anonymous):

Solve for a and b

OpenStudy (anonymous):

Each time i try with a different method i get different answers

hartnn (hartnn):

not sure whthert there is a shortcut, but the long way to do is by using elimination

hartnn (hartnn):

a= (7-b)^2 plug it in 2nd equation then square it, you will get a 4th degree polynomial in 'b' that gives you 4 values of b

OpenStudy (anonymous):

I tried it , i am getting a quadratic how do i put it under the root :0

OpenStudy (anonymous):

there are two whole number sollutions for this

hartnn (hartnn):

sqrt b = 11 - (7-b)^2 square it now

OpenStudy (anonymous):

one more thing i tried is to find the ratio between a and b yes wait

OpenStudy (anonymous):

b = 11 -49-14b+b^2

hartnn (hartnn):

a= 9, b =4 easy to eyeball

OpenStudy (anonymous):

yeah , the question says that no trial and error :)

hartnn (hartnn):

b = 11 -49-14b+b^2 <<<incorrect

hartnn (hartnn):

still incorrect :P

hartnn (hartnn):

b= (11- (7-b)^2)^2

OpenStudy (anonymous):

Ok i didn't see the root forget it

OpenStudy (anonymous):

so 4th degree plynimial creeping there

OpenStudy (anonymous):

i don't know if it helps but i got 5/3 = a/b

hartnn (hartnn):

thats incorrect, right ? given that one of the solution is 9,4

OpenStudy (anonymous):

checked it again getting the same thing

OpenStudy (anonymous):

maybe beacuse there is a root so extra sollution

OpenStudy (anonymous):

i really don't know

OpenStudy (anonymous):

I multiplied 1 st equation by a second by b

OpenStudy (anonymous):

and subtracted

OpenStudy (anonymous):

argh silly mistakes i am making tdae

OpenStudy (anonymous):

the first step is the culprit

hartnn (hartnn):

lets think of a different approach....or solve that duadric eq.

hartnn (hartnn):

*quadric

OpenStudy (anonymous):

there must be a different approach to this

hartnn (hartnn):

a and b must be perfect squares b must be less than 7 which gives b must be 1 or 4 b=1, makes a imperfect square

OpenStudy (anonymous):

great !

hartnn (hartnn):

provided a and b are real

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