F ' ( X) = 3X^2 - 18X + 15
-------------------------
3X^2 - 18X + 15 = 3 * ( X^2 - 6X + 5 )
-----------------------
X^2 - 6X + 5 = 0
D = 36 - 4*1*5 = 16
V D = 4
X1 = ( 6 + 4 ) : 2 = 5
X2 = 1
--------------------
При Y = 0
X1 = 5
X2 = 1
--------------------
X = 0
Y = 5
-------------------
89, 79, 69, 59, 49, 39, 29, 19, 9.
1) 19199=19000+100+90+9
2) 91991=90000+1000+900+90+1
3) 47803=40000+7000+800+3
4) 80080=80000+80
Вот так))