Помогите пожалуйста решить 3,4,5

3. $\frac{a^2 - b}{a}*a = \frac{a^2 - b - a^2}{a} = \frac{-b}{a} = - \frac{-5}{0.2} = -(-25) = 25$
4. $\frac{3x*(x+3) - x*(x+15) - 2*(x - 3)(x + 3)}{x*(x + 3)*(x - 3)} = \frac{3x^2 + 9x - x^2 - 15x - 2x^2 + 18}{x*(x + 3)*(x - 3)} = \frac{18 - 6x}{x*(x + 3)*(x - 3)} \\ \frac{6*(3 - x)}{x*(x + 3)*(x - 3)} = - \frac{6}{x*(x + 3)}$
5. $\frac{a^2 + 2a + 1 - 6a + 4 }{a} = \frac{a^2 - 4a + 5}{a} \\ D = 16 - 4*1*5 = - 4 \ \textless \ 0$