One of the factors of x² + y² + 2xy - z² is ?​

The factors are (x+y+z) and (x+y-z)

In other words, it factors to (x+y+z)*(x+y-z)

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Work Shown:

Notes:

In the third step, I used the rule (A+B)^2 = A^2+2AB+B^2. For this, A = x and B = y.In the last step, I used the difference of squares factoring rule A^2-B^2 = (A+B)(A-B). In this case, A = x+y and B = z.

It will be a whole number.