1. Выберите неверное равенство: А. (3b - c)(3b + c) = 9b2 – с2; В. (х+4)(4 - x) = 16 - x;
С. 36n? - 49 = (6n+ 7)(7 – 6n); D. у. — 25 = (у? – 5)(y2 + 5).
2. В выражении n? + x +0,04 замените х одночленом так, чтобы
получился квадрат двучлена:
А. 0,2n и -0,2n;
В. 4n или -4n;
С. 2n или - 2n;
D. 0,4пи -0,4n.
3. Выберите верное равенство:
А. (3 +а?)2 = 9+ За + a*;
В. (k – 5)2 = k2 - 10k + 10;
С. (х + 2у?)2 = х2 + 4 ху? + 4у; D. 16а - 24a2b + 9b2 = (8а? – 3b)2.
4. Разложите на множители выражение a4b6 – 16c8.
А. (a2b3 – 4с);
В. (a2b3 + 4с)2;
С. (a*b3 - 4с)(a2b3 + 4с.);
D. (a*b3 + 4с) (4c4 — a*b*).
5. Решите уравнение 4х2 - 25 = 0:
А. 2,5;
В. -2,5;
D. -10; 10.
С. -2,5; 2,5;
6. Разложите на множители выражение 169 - (2 +7)2;
А. (6-2)(20 + 2);
В. (6 - 2)(20 – 2);
C. (6 - 2)(2-20);
D. (2-6)(20 - 2).
Объяснение:
номер 3:
3х²-6х+с=0
а) квадратное уравнение имеет дискриминант D=b²-4ac. Если:
D>0, то уравнение имеет 2 корня (х1,2=(-b±√D)/(2a))D<0, то уравнение не имеет корнейD=0, то уравнение имеет 2 одинаковых корня (х=-b/(2a)) (необходимый нам случай)Находим дискриминант:
D=(-6)*(-6)-4*3*c=0
36-12c=0
12c=36
c=36/12
c=3
б) х=(-(-6))/(2*3)
х=6/6
х=1
номер 4:
согласно теореме Виета уравнение вида х²+рх+q=0 имеет корни х1 и х2, которые обладают следующими свойствами:
х1+х2=-р,х1*х2=qв данном случае уравнение: х²-16х+63=0, то есть p=-16, q=63, тогда:
а) х1+х2=-(-16)=16, х1*х2=63
б) 1/х1 + 1/х2 = (х2+х1)/(х1*х2)=16/63
номер 5:
х²-6х+8
а) х²-6х+8=
= х*х -2*х*3 + (3*3 - 3*3) + 8=
=(х-3)² - 9 + 8 = (х-3)² - 1
б) у(х) = х² - 6х + 8
у(х)=0, тогда
D=(-6)*(-6)-4*1*8=36-32=4=2²
x1=(-(-6)+2)/(2*1)=(6+2)/2=8/2=4
x2=(-(-6)-2)/(2*1)=(6-2)/2=4/2=2
следовательно,
х² - 6х + 8 = (х - 4) * (х - 2)
The towel on the wall… It’s our ancient custom. There was not a single Ukrainian house , which would not be decorates with towels. A house without a towel was compared with a family without children. A towel symbolized not only aesthetic taste , it was a face of a house and of a hostess. The towels proved that the hostess was tidy and hard-working.
A newly-born child was handed with the towel, guests were met with bread and salt on the towel. A son , a husband, a father were seen off with the towel. While getting married the newly-formed family was standing on a towel too. Bread and salt on an embroidered towel were a symbol of hospitality of the Ukrainian people. To take the towel , to kiss bread symbolized unity, peace, love , understanding among people. This custom has a good tradition in our country.
Towel were used in different ceremonies and in everyday life as well: for wiping a face and hands, for drying dishes, for decorating the houses, for presenting dear people. The ornaments and colours of towels were different in different regions. A lot of songs about the embroidered towel have been created in Ukraine. Объяснение: