№1.

1) (c-6)²=c²-12c+36

2) (2a-3b)²=4a²-12ab+9b²

3) (5-a)(5+a)=25+5a-5a-a²= 25-a²

4) (7x-10y)(7x+10y)=49x²+70xy-70xy-100y²=49x²-100y²

№2.

(y+4)(y-4)-7y(9+y)=y²-4y+4y-16-63y-7y²=-6y²-63y-16

№3.

(x-2)(x+2)-(x-5)²=x²+2x-2x-4-x²+10x-25 = 10x-29

№4.

(4b-9)²-(3b+8)²=16b²-72b+81-9b²-48b-64=7b²-120b+17

№5.

1) 3m-3n+(m-n)²= 3(m-n)+(m-n)²= (m-n)(3+m-n)

2) x+y+x²-y²=(x+y)+(x-y)(x+y)= (x+y)(1+x-y)

3) 9m²+6mn+n²-25=(3m+n)²-25=(3m+n-5)(3m+n+5)

4) ac^5 - c^5 -ac³+c³= c^5 (a-1) - c³(a-1)= (a-1)(c^5 - c³)= (a-1)((c³(c²-1))= (a-1)(c³(c-1)(c+1))