x⁸ + x⁷ + 1 = x⁸ + x⁷ + x⁶ - x⁶ + 1 = (x⁸ + x⁷ + x⁶) - (x⁶ - 1) =
= x⁶(x² + x + 1) - ((x³)² - 1) = x⁶(x² + x + 1) - (x³ - 1)(x³ + 1) =
= x⁶(x² + x + 1) - (x - 1)(x² + x + 1)(x³ + 1) = (x² + x + 1)(x⁶ - x⁴ + x³ - x + 1)
(3⁸×5⁸)/(3¹⁰×5⁷)=5/3²=5/9
3(5-2z)-4(z+6)=-5(2x+3)
15-6z-4z-24=-10z-15
-10z+10z=-15+9
0*z=-6
z∈∅
Корней нет
( 3b - 2)( 5 - 2b) + 6b² = 15b - 6b² - 10 + 4b + 6b² = 19b - 10