<s>[INST] What is the value of the expression $2x^2 + 3xy – 4y^2$ when $x = 2$ and $y = - 4$? What is the value of the expression $2x^2 + 3xy – 4y^2$ when $x = 2$ and $y = - 4$?
I'm not good at algebra so please explain in easy to understand steps.
Thanks
 [/INST] $2x^2 + 3xy - 4y^2$ when $x = 2$ and $y = -4$, 
$2(2)^2 + 3(2)(-4) - 4(-4)^2 = 2 *4 - 24 - 4*16 = 8 - 24 - 64 = -80$
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