дидактические материалы алгебра 7 класс Л.И. Звавич, Л.В. Кузнецова

Вариант 2

с-29

 

1. 1) a) (2x - 7) + (6x + 1) = 18;
2x - 7 + 6x + 1 = 18;
8x = 24;
x = 3;
6) 24 - 2(5x + 4) = 6;
24 - 10x - 8 = 6;
10x = 10;
x = 1;
в) (4 - 8,2х) - (3,8х + 1) = 5;
4 - 8,2х - 3,8x - 1 = 5;
12x = -2;
x = -2/12 = -1/6;
г) 12 = -6 + 6(3x - 1,5);
12 = -6 + 18x - 9;
18x = 27;
x = 1,5;
2) a) 20 + 4(2x - 5) = 14x + 12;
20 + 8x - 20 = 14x + 12;
6x = -12;
x = -2;
б) 15x - 1 = 3(7x - 1) - 2;
15x - 1 = 21x - 3 - 2;
6x = 4;
x = 4/6 = 2/3;
в) -8(11 - 2х) + 40 = 3(5х - 4);
-88 + 16x + 40 = 15x - 12;
x = 36;
г) 2х - 12(3 - х) = 1 + 3(х + 2);
2x - 36 + 12х = 1 + 3x + 6;
11x = 43;
x = 3 10/11;
3) a) -5(2 - 7x) = 0; 

 

2. 1) -3x - 11 = 0;
3x = -11;
x = -3 2/3;
2) 0,3x - 10 = 4 - 0,7x;
x = 14;
3) 3 - 6x + 16 = 2x + 3;
8x = 16;
x = 2;
4) 3(x + 1) = 5x + 12;
3x + 3 = 5x + 12;
2x = -9;
x = -4,5.
-10 + 35x = 0; 
35x = 10;
x = 2/7;
6) -5(2 - 7x) = 5; 
-10 + 35x = 5; 
35x = 15;
x = 3/7;
в) 8(5x - 1) = 0; 
40x - 8 = 0; 
40x = 8;
X = 1/5;
г) 8(5x - 1) = 8; 
40x - 8 = 8; 
40x = 16;
x = 2/5.

3. 1) a) 4(2 - 3x) + 7(6x + 1) - 9(9x + 4) = 30;
8 - 12x + 42x + 7 - 81x - 36 = 30;
51x = -51; x = -1;
б) 17 - 2(х + 3) + 5(х - 7) - 3(2x + 1) = -28;
17 - 2х - 6 + 5x - 35 - 6х - 3 = -28;
3х = 1; х = 1/3;
в) x(4x + 11) - 7(x2 - 5х) = -3x(x + 3);
2 + 11x - 7x2 + 35x = -3х2 - 9х;
55x = 0; x = 0;
2) а) n(12 - n) - 5 = 4n - n(10 + (n - 3));
12n - n2 - 5 = 4n - 10n - n2 + 3n;
15n = 5; n = 1/3;
б) 16 + 5(-с - 2(с - 4)) = 12(3 - 2с)- 1;
16 - 5с - 10с + 40 = 36 - 24с - 1;
9с = -11; с = -1 2/9.

4. 1) 2a + 11 = P1(a);
2) -1 - a = P2(а); P1(-4) = 3 = P2(-4);
P1(10) = 31; P2(10) = -11; P1(10) ≠ P2(10), не равны.