вычислите производные функций
а) (9x^3 - 7x^4 + 3x - 7)' = 9*3x^2 - 7*4x^3 + 3 = 27x^2 - 28x^3 + 3 б) [m](\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}[/m]