Вычислите: 1) 2,9+(-7.4) 2)-4,1+1,8 3)-2 1/3+(-1 7/9) 4)-1 5/6+(-3 5/12) 5)-2 1/6+(-0,9)+3 1/15 6)-1 2/15+3 5/6+(-1,7)

Вычислим чему равно выражение:

1) 2,9 + (-7,4) = 2,9 - 7,4 = 2,9 - 2,9 - 4,5 = -4,5;

2) -4,1 + 1,8 = 1,8 - 4,1 = 1,8 - 1,8 - 2,3 = -2,3;

3) -2 1/3 + (-1 7/9) = -2 1/3 - 1 7/9 = -(2 1/3 + 1 7/9) = -((2 * 3 + 1)/3 + (1 * 9 + 7)/9) = -(7/3 + 16/9) = -((7 * 3)/9 + 16/9) = -(21/9 + 16/9) = -47/9 = -5 2/9;

4) -1 5/6 + (-3 5/12) = -1 5/6 - 3 5/12 = -1 - 3 - 5/6 - 5/12 = -4 - 10/12 - 5/12 = -4 - (10 + 5)/12 = -4 - 15/12 = -4 - 1 3/12 = -5 3/12 = -5 1/4;

5) -2 1/6 + (-0,9) + 3 1/15 = -2 + 3 + 1/6 - 9/10 + 1/15 = 1 + 5/30 - 27/30 + 2/30 = 1 - 20/30 = 1 - 2/3 = 3/3 - 2/3 = 1/3;

6) -1 2/15 + 3 5/6 + (-1,7) = -1 + 3 - 1 - 2/15 + 5/6 - 7/10 = 1 - 4/30 + 25/30 - 21/30 = 1.