Question

26 . Упростите выражение и найдите его числовое значение:
1) 5 (3х – 7) + 2 (1 - x) при х =1/26 ;
2) 7(10 – x) + 3(2x – 1) при х = -0,048;
3) 1/3 (6x – 3) +2/5 (5х – 15), при х = 3,01;
4) 0,01(2,2x – 0,1)+0,1(x - 100), при x = -10.​

Answer 1

Ответ:

$1)5 \times (3x - 7) + 2 \times (1 - x) = 15x - 35 + 2 - 2x = 13x - 33 \\ 13 \times \frac{1}{26} - 33 = \frac{1}{2} - 33 = - \frac{65}{2} = - 32 \frac{1}{2}$

$2)7(10 - x) + 3(2x - 1) = 70 - 7x + 6x - 3 = 67 - x \\ 67 - ( - 0.048) = 67 + 0.048 = 67.048$

$3) \frac{1}{3} (6x - 3) + \frac{2}{5} \times (5x - 15) = \frac{1}{3} \times 3(2x - 1) + \frac{2}{5} \times 5(x - 3) = (2x - 1) + 2(x - 3) = 2x - 1 + 2x - 6 = 4x - 7 \\ 4 \times 3.01 - 7 = 12.04 - 7 = 5.04$

$4)0.01(2.2 x- 0.1) + 0.1(x - 100) = 0.022x - 0.001 + 0.1x - 10 = 0.122x - 10.001 \\ 0.122 \times ( - 10) - 10.001 = - 1.22 - 10.001 = - 11.221$