3(2-y)²-4(y+5)²
=3(4-4y+y²)-4(y²+10y+25)
=12-12y+3y²-4y²-40y-100
=-y²-52y-88
5(a-1)²-10(1-a)
=5(a-1)²+10(a-1)
=(a-1)(5a-5+10)
=(a-1)(5a+5)
=5(a-1)(a+1)
3(2-y)²-4(y+5)²
=3(4-4y+y²)-4(y²+10y+25)
=12-12y+3y²-4y²-40y-100
=-y²-52y-88
5(a-1)²-10(1-a)
=5(a-1)²+10(a-1)
=(a-1)(5a-5+10)
=(a-1)(5a+5)
=5(a-1)(a+1)