№13. Упростите выражение: 1) -2,3 · 4c; 2) - 0,96 · (-0,6); 3) -5a · 3,6b; 4) -8x · (-0,5y) · 0,6l; 5) -\(\frac{8}{21}\)z · (-t) · \(\frac{7}{24}\); 6) 2\(\frac{2}{7}\)m · \(-\frac{21}{64}n\).

Решение:

1. 
   

   1) \( -2.3 \times 4c = -9.2c \)

   
   

   2) \( -0.96 \times (-0.6) = 0.576 \)

   
   

   3) \( -5a \times 3.6b = -18ab \)

   
   

   4) \( -8x \times (-0.5y) \times 0.6l = 4xy \times 0.6l = 2.4xyl \)

   
   

   5) \( -\frac{8}{21}z \times (-t) \times \frac{7}{24} = \frac{8 \times 7}{21 \times 24} zt = \frac{56}{504} zt = \frac{1}{9} zt \)

   
   

   6) \( 2\frac{2}{7}m \times (-\frac{21}{64}n) = \frac{16}{7}m \times (-\frac{21}{64}n) = -\frac{16 \times 21}{7 \times 64} mn = -\frac{16 \times 3 \times 7}{7 \times 4 \times 16} mn = -\frac{3}{4} mn \)

   
   

Ответ: 1) -9.2c; 2) 0.576; 3) -18ab; 4) 2.4xyl; 5) \(\frac{1}{9}\)zt; 6) -\(\frac{3}{4}\)mn.