найти производную
а) f(x)=(9x+1)(2x-5)
б) f(x)=4-6x/3x+1

а) f(x)'=((9x+1)(2x-5))' = (18x²-43x-5)' = 36x - 43

б) f(x)'=(4-6x/3x+1)' = (4-2+1)' = (3)' = 0