The second unit function of mathematics test paper in senior one and its answer to volume B.
(1) let f(x)=ax+b then f(f(x))=a(ax+b)+b=a? x+ab+ba？ =9..①ab+b=8。 ② From ① ②, a=3, B = 2；; If a=-3 and b=-4, then f(x)=3x+2 or f (x) =-3x-4 (2) f (2x+1)) = 8x-7f (f (2x+1)) = 4 (2x