4. Show that მ2 მ2 + მ2 მy2 = 4. მ2 อะอะ Deduce the following, for a smooth complex-valued function h (a) h is harmonic if and only if a2h/azz = 0. (b) h is harmonic if and only if Əh/Oz is analytic. (c) h is harmonic if and only if ah/az is conjugate-analytic 4. Show that მ2 მ2 + მ2 მy2 = 4. მ2 อะอะ Deduce the following, for a smooth complex-valued function h (a) h is harmonic if and only if a2h/azz = 0. (b) h is harmonic if and only if Əh/Oz is analytic. (c) h is harmonic if and only if ah/az is conjugate-analytic