Вправи: 1224

1224. Обчисліть зручним способом:

1) –247 • 129 + 547 • 129 = 129 • (547 – 247) = 129 • 3 = 123;

2) 49 • 238 – 158 • 49 – 78 • 49 = 49 • (238 – 158 – 78) = 49 • (238 – 248) = 49 • (–18) = –118.

3) 28 • (14 – 27 + 314 – 528) = 28 • 14 – 28 • 27 + 28 • 314 – 28 • 528 = 7 – 8 + 6 – 5 = 0;

4) (234 – 156 + 213) • (–12) = (114 – 116 + 73) • (–12) = 114 • (–12) – 116 • (–12) + 73 • (–12) = 11 • (–3) – 11 • (–2) + 7 • (–4) = –33 + 22 – 28 = –60 + 22 = –38.