5ab-b²+25a-5b=b(5a-b)+5(5a-b)=(5a-b)(b+5)
12 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Решение смотри на фотографии
15х+15=0
15х=-15
х=-15:15
х=-1
= - x^5 + 15x^4 - 90x^3 + 270x^2 - 405x + 243