給出下列三個(gè)等式：f(xy)＝f(x)·f(y)，f(x＋y)＝f(x)·f(ｙ)，f()＝f(x)－f(y)．下列函數(shù)中不滿足其中任何一個(gè)等式的是

f(x)＝3x

f(x)＝x^－1

f(x)＝3^x

f(x)＝log₂x

給出下列三個(gè)等式：f(xy)＝f(x)＋f(y)，f(x＋y)＝f(x)f(y)，f(x＋y)＝f(x)＋f(y)，下列函數(shù)中不滿足其中任何一個(gè)等式的是

f(x)＝3^x

f(x)＝x^a

f(x)＝log₂x

f(x)＝kx(k≠0)