1) 5+a/2a^2+1-2a/a; 2)4x+8/12x^3•3x/x+2; 3) (m+n)^2:m^2-n^2/8m; 4) 2-b/b+b-3/3b^2; 5)3c+9/6c•2c^4/c+3; 6)x^2-y^2/6y:(x-y)^2