1). (2x-1)^2=4x^2-4x+1
(3a+c)^2=9a^2+6ac+c^2
(y-5)(y+5)=y^2-25
(4b+5c)(4b-5c)=16b^2-25c^2
2).(x+y)(x-y)-(x^2+3y^2)=x^2-y^2-x^2-3y^2=-4y^2
3).16y^2-0,25=(4y-0,5)(4y+0,5);
a^2+10ab+25b^2=(a+5b)^2
4).(5-x)^2-x(2,5+x)=0
25-10x+x^2-2,5x-x^2=0
-12,5x+25=0
-12,5x=-25
x=2
5).(2a-b^2)(2a+b^2)=4a^2-b^4;
(x-6x^3)^2=x^2-12x^3+36x^6;
(y+b)^2 (y-b)^2= (y^2-b^2)^2
6).(5x-2)(5x+2)-(5x-1)^2=4
25x^2-4-(25x^2-10x+1)=4
25x^2-4-25x^2+10x-1-4=0
10x-9=0
10x=9
x=0,9;
100x^2-16=0
(10x-4)(10x+4)=0
10x-4=0 U 10x+4=0
10x=4 U 10x=-4
x=0,4 U x=-0,4
7). (1/81)a^2-0,09c^4=[(1/9)a-0,3c^2][(1/9)a+0,3c^2];
(b+8)^2-4b^2=(b+8-2b)(b+8+2b)=(8-b)(8+3b)