Сократите дробь а) 15mk^4/k^2; б) 4a/a2-4a; в) x^2-y^2/x-y.

x/2,5=-6,2/15

15x=-15,5

x=-31/30=- 1 1/30

i'm not sure that's right, but folowing my minds:

as k+k=t and t+t=k it means that t=k. so it doesn't matter what number to substitute for letters, and c=0. hope, i helped you=)