....................................................................................
(x2 - 6x - 21) (x3 - 6x) + 80 = 0
x4 - 12x3 +15x2 + 126x + 80 = 0
(x-8)(x+2)(x2 - 6x - 5) = 0
x-8 = 0
x+2=0
x2 - 6x - 5 =0
x=8
x= - 2
x2 - 6x = 5 x2 - 6x + 9 = 14 (x-3)2 = 14 х = 3 + √14 или х-3= - <span>√14</span>
Точно не знаю, но как мне кажется 345,5 см
3а+7b
3×(-0.2)+7×0.7= 4.3
3×1,5+7×(-0.2)=3.1
4.3>3.1