Homogeneous function - is it?

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Alpha Chiang's book - Fundamental Methods of Mathematical Economics presents a question:

Is this homogeneous? If so, of what degree?

  1. f(x,y) = ($x^2 - y^2)$$^0.^5$

My main issue is how to simplify it in order to multiply it by constant and find the answer.

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Yes it is; to see this, substitute $tx, ty$ in for $x, y$ to get $$f(tx,ty) = \sqrt{(tx)^2 - (ty)^2} = \sqrt{t^2x^2 - t^2y^2} = \sqrt{t^2(x^2 - y^2)} = t\sqrt{x^2-y^2} = t\cdot f(x,y). $$ Thus by definition $f$ is homogenous of degree $1$ since $t^1$ could be pulled out of the equation.