Question

what should be added to x2+xy+y2 to obtain 2x2+4xy​

Answer 1

Answer:

x² + 3xy - y².

Step-by-step explanation:

Let the unknown number be z.

z + x² + xy + y² = 2x² + 4xy

z + y² = x² + 3xy

z = x² + 3xy - y²

Answer 2

$x {}^{2} + xy + y {}^{2} \: to \: obtain \: 2x {}^{2} + 4xy$

$x {}^{2} + 3xy - y {}^{2} \: should \: be \: added$