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If (2x+3y)^2 = 4 and xy = -5, what is the value of 4x^2 + 9y^2

 Oct 9, 2020
 #1
avatar+27725 
+1

(2x+3y)^2 = 4     expand

4x^2    +   12 xy   + 9y^2    = 4

4 x^2    + 12(-5)   + 9y^2   = 4        You can take it from here, hopefully !

 Oct 9, 2020
 #2
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well i got that already i got 4x + 9y = 64 but i dont understand how to turn this into 4x^2 + 9y^2 = something?

Guest Oct 9, 2020
 #3
avatar+27725 
+1

Well, if you got   4x + 9y = 64    you didn't look at the answer I gave you......

ElectricPavlov  Oct 9, 2020
 #4
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Ok i got it right thank you! i understood my mistake was i forgot that when simplifying (2x+3y)(2x+3y) i just multiplyed out the integers but i forgot that the variables also square each other. 

Guest Oct 9, 2020
 #5
avatar+27725 
0

Yay !

ElectricPavlov  Oct 9, 2020

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