1) (x+2y) ² 2) 25t²-(2z+3t)² 3) -c (-d-3)² 4) 3 (2a+5)²+5 (2a-3)²

1) x²+2x+2y+(2y)²
x²+4xy+4y²
2) (5t-(2z+3t))•(5t+(2z+3t))
(5t-2z-3t)•(5t+2z+3t)
(2t-2z)•(8t+2z)
2(t-z)•2(4t+z)
2•2(t-z)•(4t+z)
4(t-z)•(4t+z)
3) -c•(-(d+3))²
-c•(d+3)²
-c•(d²+6d+9)
-cd²-6cd-9c
4) 3(4a²+20a+25)+5(4a²-12a+9)
12a²+60a+75+20 a²-60a+45
32a²+120.