4.
[tex]5a - 2 - 3a + 6 + 4a - 2 = 6a+2\\\\dla \ \ a = -2\\\\6a+2 = 6\cdot(-2)+2 = -12+2 = -10[/tex]
5.
[tex]-x^{5}\\\\4x^{2}\\\\-3xy[/tex]
