X ^ 2 + 2XY - ^ 2 = 2x, derivative The result is 2x + 2Y + 2XY '- 2yy' = 2, but how does - 2yy 'come from?

X ^ 2 + 2XY - ^ 2 = 2x, derivative The result is 2x + 2Y + 2XY '- 2yy' = 2, but how does - 2yy 'come from?

x^2+2xy-y^2=2x
2x+2y+2xy'-2y*y'=2
The derivation of Y ^ 2 is based on the derivation of compound function,
If the outer derivative is 2Y, it is also multiplied by the derivative y'of y