вычислите производные функций
а) (9x3 – 7x4 + 3x – 7)' = 9·3x2 – 7·4x3 + 3 = 27x2 – 28x3 + 3 б) (\frac{3x+1}{5-3x})' = \frac{(3x+1)'(5-3x) - (3x+1)(5-3x)'}{(5-3x)^2} = \frac{3(5-3x) - (3x+1)(-3)}{(5-3x)^2} = \frac{15-9x + 9x+3}{(5-3x)^2} = \frac{18}{(5-3x)^2}