Номер 4 а)(2-3n)^2-9n^4;4-12n+9n^2-12n+4;-9n^2(n^2-1) -4 (3n-1);-9n^2-4(n^2-1)(3n-1)
б) (a-5)^2+10-2a+1; a^2-10a+25+10-2a+1;a^2-12a+36;(a-6)^2.
в) x^6-x^4-x^2+1; x^2(x^3-x^2-1)+1.
5. 87^2-13^2/91^2-34*91+17^2=(87+13)(87-13)/(91-17)(91-17)=7400/5476=1850/1369.
6. (x-3)^2+(3-x)(x+3)=(x+2)^2-x^2
x^2-6x+9+3x+9-x^2-3x-x^2-4x-4+x^2=0
-10x=-14
x=1,4
вот,