Запиши данное выражение без скобок. (−21)+(+72)+(−103)=

1)1.7-14=-7                                                                                                                                                         2.-28:-7=4                                                                                                                                                            3.4-10=-6                                                                                                                                                            задача а: 36*2/9=8 лет                                                                                                                                    задача б: 5:4*100=125%                                                                                                                                задача в 40%=20 слов                           40%=0,4                                                                                         20:0,4=50 слов                                                                                                                                                  10(1-0,2у)-(1-у)=17                                                                                                                                            10-2у-1+у=17                                                                                                                                                      9-у=17                                                                                                                                                                   у=9-17=-8                                                                                                                                                            щас остальные ответы напишу                                                                                                               задача:60 + 8=68км/час - второй поезд                                                                                               24*1/3=8 часов-ехали поезда                                                                                                                 60*8+68*8=1004 км                                                                                                                                   задача:72-12=60м-стала длина забора                                                                                              26-7=19м-стала ширина забора                                                                                                            60*19=1140 м2

Задание удобно решать графически.Надо начертить график ф-ции у=|x-1|+|x+1| и у=а.

Знаки |x-1| - - - (-1) - - - (1) + + +

Знаки |x+1| - - - (-1) + + + (1) + + +

Рассматриваем три интервала.

-∞<х≤ -1 ⇒ у=-х+1-х-1=-2х Строим эту прямую y=-2x при х∈(-∞,-1].

-1<x≤1 ⇒ y=-x+1+x+1=2 ⇒Прямую у=2 строим при х∈(-1,1]

1<х<∞ ⇒у=х-1+х+1=2х . Строим прямую у=2х при х∈(1,∞)

Прямые строят только в тех пределах изменения переменной х, в которой это указано.Остальные части прямых стирают.

По графику будет видно, что прямая у= а,которая параллельна оси ОХ не будет перес екать график ф-ции у=|x-1|+|x+1| при а<2.А значит, при а<2 уравнение не имеет корней