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could someone plss answer this..
x^2+2y^2=17,  
 x^2-y^2 = 5  the "^2" indicate as a "raise to 2". i want to solve for x and y in quadratic equation in two unknowns
TNX!
^_^


Sagot :

Multiply the equation [tex] x^{2} [/tex] - [tex] y^{2} [/tex] = 5  by -1 then
Add both equation:
  (  [tex] x^{2} [/tex] + [tex] 2y^{2} [/tex] = 17 )
+( [tex] -x^{2} [/tex] + [tex] y^{2} [/tex] = -5 )
=  [tex] 3y^{2} [/tex] =12
 = [tex] y^{2} [/tex] = 12/ 3
= [tex] y^{2} [/tex] = 4
[tex] \sqrt{ y^{2} } [/tex] = [tex] \sqrt{4} [/tex]
 y = 2 


 Substitute it to any of the equation:
[tex] x^{2} [/tex] - [tex] y^{2} [/tex] = 5
[tex] x^{2} [/tex] - [tex] 2^{2} [/tex] = 5
[tex] x^{2} [/tex] - 4 = 5
[tex] x^{2} [/tex] = 9
[tex] \sqrt{ x^{2}} [/tex] = [tex] \sqrt{9} [/tex]
 x = 3