f（-3）=log2[(根号下x2+1)-x]+g(x)-2的x 次方 (后面不应该是等号,我假设是减号)
=log2(根号10+3)+g(-3)-1/8=41/8
求出g(-3)=21/4-log2(根号10+3)
f(3)=log2(根号10-3)+g(3)-8=log2(根号10-3)-8-g(-3)
=log2(根号10-3)-8-[21/4-log2(根号10+3)]
=-53/4