Завдання:
Розкрий дужки і зведи подібні доданки:
1) –4(7 – 2x) + 6(3x – 5);
2) 2(a – 2b) – 7(2a + 3b);
3) (3m – 2) ⋅ (–0,7) + (4 – 2m) ⋅ 0,5;
4) 4,2(5x – 2y) – 2,7(3x – y).
Розв'язок:
1) -4(7 – 2х) + 6(3х – 5) = -4 ⋅ 7 – 4 ⋅ (-2х) + 6 ⋅ 3х – 6 ⋅ 5 = -28 + 8х + 18х – 30 = 26х – 58
2) 2(a – 2b) – 7(2a + 3b) = 2a – 2 ⋅ 2b – 7 ⋅ 2a – 7 ⋅ 3b = 2a – 4b – 14a – 21b = -12a – 25b
3) (3m – 2) ⋅ (-0,7) + (4 – 2m) ⋅ 0,5 = 3m ⋅ (-0,7) – 2 ⋅ (-0,7) + 4 ⋅ 0,5 – 2m ⋅ 0,5 = -2,1m + 1,4 + 2 – m = -3,1m + 3,4
4) 4,2(5x – 2y) – 2,7(3x – y) = 4,2 ⋅ 5x – 4,2 ⋅ 2y – 2,7 ⋅ 3x – 2,7 ⋅ (-y) = 21x – 8,4y + 2,7y = 12,9x – 5,7y