21. 21m + 19m = (21 + 19)m = 40m22. -13n - 3,2n = (-13 - 3,2)n = -16,2n23. -62x² + 15x² = (-62 + 15)x²= -47x²24. 16y² - 48y² = (16 - 48)y² = -32y²25. 27x²y -0,9x²y=26,1x²y26. -5a²·(-21a²) = 105a⁴27. 1,2b·6b² = 7,2b¹·b²=7,2b¹⁺²=7,2b³28. 63ab·(-2а) = -126a²b29. 21b·ас=21abc30. -Зmn²·17mn = -51m²n²·n¹ = -51m²n²⁺¹ = -51m²n³
21. 21m + 19m = (21 + 19)m = 40m
22. -13n - 3,2n = (-13 - 3,2)n = -16,2n
23. -62x² + 15x² = (-62 + 15)x²= -47x²
24. 16y² - 48y² = (16 - 48)y² = -32y²
25. 27x²y -0,9x²y=26,1x²y
26. -5a²·(-21a²) = 105a⁴
27. 1,2b·6b² = 7,2b¹·b²=7,2b¹⁺²=7,2b³
28. 63ab·(-2а) = -126a²b
29. 21b·ас=21abc
30. -Зmn²·17mn = -51m²n²·n¹ = -51m²n²⁺¹ = -51m²n³