[tex]a).5x*3x+4x*x-3x^2*3+x^2= \\ =15x^2+4x^2-6x^2+x^2= \\ =19x^2-6x^ 2+x^2= \\ =13x^2+x^2= \\ =14x^2 \\ b).a*2a-3a^2*2+6a*5a-4*3a^2+8a^2= \\ =2a^2-6a^2+30a^2-12a^2+8a^2= \\ =-4a^2+30a^2-12a^2+8a^2= \\ =26a^2-12a^2+8a^2= \\ =14a^2+8a^2= \\ =22a^2[/tex]