设偶函数F(X)对任意X属于R,都有F（X)F(X+3)+17=0,且X属于【-3,-2】是,F(X)=2X,则F(113.5)=?

当x属于【-3,-2】时,f(x)=2x,故当x属于【2,3】时,f(x)=-2x,f(2.5)=5又f(x+3)=-17/f(x),则f(x+6)=-17/f(x+3)=-17/(-17/f(x))=f(x),故f(113.5)=f(18*6+5.5)=f(5.5)=-17/f(2.5)=-17/5