va rogggggg este urgent

Răspuns:
a)3a^2-3=3(a^2-1)
b)7x^2-28=7(x^2-4)
c)5x^2-20=5(x^2-4)
d)0.5-0.5c^2=0?5(1-c^2)
e)a^2n^2-n^2=n^2(a^2-1)