1) 5а-(1+5a^2)/a= (5a^2-1-5a^2)/a= -1/a
2)(a-b)/(a+b)-(a+b)/(a-b)=((a-b)^2-(a+b)^2)/(a+b)(a-b)=((a-b-a-b)(a-b+a+b))/(a+b)(a-b)=(-2b*2a)/(a+b)(a-b)=-4ab/a^2-b^2
3) (3a-6/2c)*(4c/a-2)= (3(a-2)*4c)/2c*(a-2)= 3*2=6
4)(a^2-b^2/c^2):(a-b/c)=((a-b)(a+b)*c)/(a-b)*c^2= (a+b)/c
5) x+5/24- 3x-8/16= (3x+15-6x+16)/24=(-3x+21)/24= -3(x-7)/24=-(x-7)/8