вычислите с подмогою формулы а^2-b^2= (a-b)(a+b) 1) 20^2-19^2 2)3,5^2-3,7^2 3)(7/9)^2-(1/6)^2

Ответ:

1) 39;

2) -1,44;

3) 187/324;

4) -11/20;

5) 0;

6) -27 3/36;

7) 800

Пошаговое разъясненье:

1) 20 - 19 = (20 - 19)(20 + 19) = 1 * 39 = 39;

2) 3,5 - 3,7 = (3,5 - 3,7)(3,5 + 3,7) = (-0,2) * 7,2 = -1,44;

3) (7/9) - (1/6) = (7/9 - 1/6)(7/9 + 1/6) = 11/18 * 17/18 = 187/324;

4) (3/10) - (4/5) = (3/10 - 4/5)(3/10 + 4/5) = -1/2 * 11/10 = -11/20;

5) (2 1/7) - (2 1/7) = (2 1/7 - 2 1/7)(2 1/7 + 2 1/7) = 0 * 4 2/7 = 0;

6) (5 1/6) - (7 1/3) = (5 1/6 - 7 1/3)(5 1/6 + 7 1/3) = -13/6 * 75/6 = -27 3/36;

7) 54 - 46 = (54 - 46)(54 + 46) = 8 * 100 = 800