2.a = (3*k+2+k^2-3*k)/k=(2+k^2)/k^2

2.b = (5a+10-4a)/(a^2+2) = (a+10)/(a^2+2)

3     = (2*x^2-y-2*x^2)/2*x = -y/2*x, полставляем -(-8)/2*0.4 = 10

4    =(x^2-9+15-x-x^2+3*x)/(x^2-9)=(2*x+6)/(x^2-9) = [2*(x+3)]/[(x-3)*(x+3)]=2/(x-3)