+0  
 
0
177
1
avatar

If  $x + 2y= 4$ and $xy = -8$, what is the value of $x^2 + 4y^2$  

 May 1, 2021
 #1
avatar+121047 
+1

x + 2y  =  4     

xy = -8

 

Square both sides of the  the first equation

 

x^2  + 4xy + 4y^2  =    16

 

x^2  + 4(-8)  + 4y^2  =  16

 

x^2  + 4y^2  -32  =  16

 

x^2 + 4y^2  =  16 + 32

 

x^2  + 4y^2  =  48

 

coolcoolcool

 May 1, 2021

32 Online Users

avatar
avatar