1. От перестановки мест слагаемых сумма не меняется

2. а) –(–8) + 3 = 8 + 3 = 11

б) –(12 + (–1)) = –(12 – 1) = –(11) = –11

в) –(–10) + (–6) = 10 – 6 = 4

г) –((–3) + 1)= –(–3 + 1) = – (–2) = 2

д) –((–20)+(–10)) = –(–20 – 10) = –(–30) = 30

е) –(–(6+4)) = –(–10) = 10

3. а) –(3+8) = – 11;

(–3) + (–8) = –3 – 8 = –11 или (–3) + (–8) = –(3+8) = – 11

значения выражений равны

б) –(6+1) = –7;

(–6) + (–1) = –6 – 1 = –7 или (–6) + (–1) = –(6+1) = –7

в) –((–10) + (–5)) = –(–10 – 5) = –(–15) = 15

10 + 5 = 15

4. a + b

20 + 15 = 35

(–20)+(–15) = – 20 — 15 = – 35

(–20) + 15 = —20 + 15 = –5

20 +(–15) = 20 – 15 = 5

–(a + b)

–(20 + 15) = –35

–((–20)+(–15)) = –(–20 – 15) = –(–35) = 35

–((–20) + 15) = –(–20 + 15) = –(–5) = 5

–(20 + (–15)) = –(20 – 15) = – (5) = –5

(–a) + (–b)

(–20) + (–15) = –20 – 15 = – 35

(–(–20)) + (–(–15)) = 20 + 15

(–(–20)) + (–15) = 20 – 2 =15

(–20) + (–(–15)) = –20 + 15 = –5