Площадь прямоугольника равна 14см в квадрате, длина - 7 см.найдите ширину и периметр прямоугольника

a=7 b-

s=ab   7b=14   b=2   см

p=2(a+b)=2(7+2)=18 см

s=a*b

14 = 7*b

b = 14 / 7 =2 (см) - ширина

 

p = 2*(a+b)=2*(7+2)=2*9=18 (см)

1.в

2.в

3.в

4.б

5.б

6.а

7.а) x1=0; x2=6;     б) x1=-0,4; x2=0,4;

8.(2x+9)*(x-1)=0

x1= -4.5; x2= 1;

9. x^2-5x+4

10. (3x+1)^2=4x^2+5x-1

5x^2+5x+2=0

дискриминант отрицательный.

11. x1=-4; x2=-3; x3=3; x4=4;

12. За т. Вієта сума коренів квадратного рівняння дорівнює другому коефіцієнтові, взятому із протилежним знаком (тобто, x_1+x_2=14)  

Формулу x_1^2+x_2^2 можна представити як (x_1+x_2)^2-2x_1*x_2, але для цього ми маємо знати ще добуток коренів.  

Добуток коренів (знову-таки за т. Вієта) дорівнює третьому коефіцієнтові (тобто, x_1*x_2=5)  

Підставимо значення у формулу: (x_1+x_2)^2-2*x_1*x_2=14^2-2*5=196-10=186

Let's take a look at what it's really like to live in space.2)   first of all, you can forget about having a nice hot shower in the morningy. astronauts have to use a vacuum hose to wash with.   so the residents of the iss actually spend 2 hours a day working out on exercise bikes and rowing machines.3) there's no escape from household chores on the iss. as dangerous bacteria grow quickly in zero gravity, the astronauts clean the whole station every day,   also the lack of gravity makes the simplest things in life seem quite weird! the astronauts simply put their dirty dishes and rubbish into plastic bags and send them back to earth.4) the astronauts could sleep anywhere, but they can't risk bumping into any computer controls so they strap themselves into a sleeping bag on the wall.it's important to cover your eyes, however, to block out the light of the sun as the sun rises and sets every 45 minutes when you are orbiting the earth. 5)   they often send emails back home, read books or watch movies, but most of all they like to stare out of the window and take pictures of their real home, earth!