Ответ:

1.

1) (x+5)^2=x^2+10x+25

2) (3y-x)^2=9y^2-6yx+x^2

3) (4-x)^2=16-8x+x^2

4) (6x+2)^2=36x^2+24x+4

2.

a) (a-3)(a+3)=a^2-3^2

б) (2y+5)(2y-5)=2y^2-5^2

3.

1) x^2-81=(x+9)(x-9)

2) 49-y^2=(7+y)(7-y)

3) x^2-9/25=(x+3/5)(x-3/5)

4) 0.09-c^2=(0.3+c)(0.3-c)