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x=2y and x^2+2x-y-y^2=36

 Dec 7, 2017

Best Answer 

 #1
avatar+28182 
+1

x=2y  (1)

x^2+2x-y-y^2=36 (2)

 

Replace x in (2) by 2y

 

4y^2 +4y -y - y^2 = 36

3y^2 + 3y = 36

y^2 + y = 12 

y^2 + y - 12 = 0

(y + 4)(y - 3) = 0

 

Hence (i) y = -4, and using (1) x = 2*(-4) or x = -8

and     (ii) y = 3, and using (1) x = 2*3 or x = 6

 Dec 7, 2017
 #1
avatar+28182 
+1
Best Answer

x=2y  (1)

x^2+2x-y-y^2=36 (2)

 

Replace x in (2) by 2y

 

4y^2 +4y -y - y^2 = 36

3y^2 + 3y = 36

y^2 + y = 12 

y^2 + y - 12 = 0

(y + 4)(y - 3) = 0

 

Hence (i) y = -4, and using (1) x = 2*(-4) or x = -8

and     (ii) y = 3, and using (1) x = 2*3 or x = 6

Alan Dec 7, 2017

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