1,8+7t-10t^2 больше или рано 3

получается ответ 0,1

1,8+7t-10t^2 >= 31,8+7t-10t^2 -3 >= 0-10t^2+ 7t - 1.2 >= 0-10t^2+ 7t - 1.2 = 0D = 49 - 4*(-10)*(-1.2) = 49 - 48 = 1t1 = (-7+1)/-20 = 6/20 = 3/10t2 =  (-7-1)/-20 = 8/20 = 2/5-10(t-3/10)(t-2/5) >= 03/10 <= t <= 2/5