1)the two friends lived in liverpool, didn't they? 2)the boys didn't like doing sums, did they? 3)the river mersey was far busier in the old days, wasn't it? 4)the narrator's relatives had seen a lot of parts of the globe, hadn't they? 5)the boys were not teenagers at the time, were they? 6)the boys tried to plan their voyage, didn't they? 7)the boys didn't prepare food and drink for their voyage, did they? 8)the boys could easily get on board the ship, couldn't they? 9)the boys had to give themselves up after midge got sick, didn't they? 10)the narrator's parents didn't believe his story, did they?
4b(5a-b)-(5a-2)(5a+2)=20ab-4b²-(25a-4)=20ab-4b²-25a+4=-4b²+20ab-25a²+4 = -(4b²-20ab+25a²)+4= -(2b-5a)²+4 любое действительное число в квадрате всегда больше либо равно нулю, то есть (2b-5a)²≥0, значит -(2b-5a)²≤0 следовательно для выражения -(2b-5a)² наибольшем значением будет 0, следовательно для выражения -(2b-5a)²+4 наибольшим будет 0+4=4 ОТВ: 4
2) 2a²-2ab+b²-2a+2=а²+а²-2ab+b²-2a+2=(а²-2ab+b²)+a²-2a+2= (a-b)²+(a²-2a+2) выше уже было сказано: (a-b)²≥0 рассмотрим функцию у=a²-2a+2 - парабола найдем нули a²-2a+2=0 D=4-4*2=-4<0 Дискриминант <0, ветви параболы направлены вверх, значит наименьшее значение будет в вершине параболы:
360:40=9
360:9=40