F ' (x) = 27x^3 - 1
f ' (x) = 0
27x^3 - 1 = 0
27x^3 = 1
x^3 = 1/27
x = 1/3
f (1/3) = 1,75 -- минимум
<span>(5-6x)(5+6x)-25(1-3x)
</span>25-36*x^2-25+75х
75*x-36*x^2
3 15 9
-- х --- = --
20 1 4
7 15 7
-- х -- = --
30 1 2
9 14 23
--- + --- = ---
4 4 4
23
--
ответ 4
519,4:(29,3+х)=14
Домножим на (29,3+х)
519.4=14(29,3+х)
519.4=410,2+14х
109,2=14х
Х=7,8