т.к. а^2-b^2=(a-b)*(a+b), mo
1)..=20^2-m^2=(20-m)*(20+m)
2)...=(2x-5)(2x+5)
3)...=(5/3t)^2-1^2=(5t/3-1)(5t/3+1)
4)...=(4a^2)^2-9^2=(4a^2-9)(4a^2+9)=(2a-3)(2a+3)(4a^2+9)
5)...=(x+1-4)(x+1+4)=(x-3)(x+5)
т.к. a^2-2ab+b^2=(a-b)^2, a a^2+2ab+b^2=(a+b)^2, mo
6)...=(a-6)^2
7)...=25m^2+24mn=m(25m+24n)