Найдите значение а, если: 1) -а= - (0,75 - 5/12) 2) -а= 1 7/8 * (5 8/15 + 2 1/3)

1) –а = -(0,75 - 5/12);

-а = -0,75 + 5/12;

-а = -75/100 + 5/12;

-а = (-75 * 3) / (100 * 3) + (5 * 25) / (12 * 25);

-а = -225/300 + 75/300;

-а = -150/300;

-а = -1/2;

а = 1/2. Проверка:

-1/2 = -(0,75 – 5/12);

-1/2 = -0,75 + 5/12;

-1/2 = -75/100 + 5/12;

-1/2 = (-75 * 3) / (100 * 3) + (5 * 25) / (12 * 25);

-1/2 = -225/300 + 75/300;

-1/2 = -150/300;

-1/2 = -1/2. Решение выполнено верно.  

2)  -а = 1 7/8 * (5 8/15 + 2 1/3);

-а = 1 7/8 * (83/15 + 7/3);

-а = 1 7/8 * (83/15 + (7 * 5) / (3 * 5));

-а = 1 7/8 * (83/15 + 35/15);

-а = 1 7/8 * 118/15;

-а = 15/8 * 118/15;

-а = (15 * 118) / (8 * 15);

-а = 1770/120;

-а = 59/4;

-а = 14 3/4;

а = -14 3/4. Проверка:

- (-14 3/4) = 1 7/8 * (5 8/15 + 2 1/3);

14 3/4 = 1 7/8 * (83/15 + 7/3);

14 3/4 = 1 7/8 * (83/15 + (7 * 5) / (3 * 5));

14 3/4 = 1 7/8 * (83/15 + 35/15);

14 3/4 = 1 7/8 * 118/15;

14 3/4 = 15/8 * 118/15;

14 3/4 = (15 * 118) / (8 * 15);

14 3/4 = 1770/120;

14 3/4 = 59/4;

14 3/4 = 14 3/4. Решение верно.