по теореме Виета
x1+x2= 17
x1*x2= 72
1/x1+1/x2= (x1+x2)/x1*x2= 17/72
.......................................
(5x-9)²≥(9x-5)²
25x²-90x+81≥81x²-90x+25
25x²-81x²≥25-81
-56x²≥-56
-x²≥-1
x²≤1
x∈/-1,1/, -1≤x≤1
- ( - 9x) - (8 + 7x) = 2(x - 4)
9x - 8 - 7x = 9x - 7x - 8 = 2x - 8
2x - 8 = 2x - 8
Является
================================
<span>2 √7примерно 5,29150</span>