Упростите выражение: [424] a) 6x + 3y - 3.c - 4y; в) 4a2 - 2b2 - 9a2 + 2b2; 6) - + + acd; г) -0,3п2 - 2,8n + n2 + 1,8n.

№ 1.  (8 4/5 - 13,8 : 3 5/6) · 12/13 = 4 целых 4/5 = 4,8.

1) 13,8 : 3 5/6 = 138/10 : 23/6 = 69/5 · 6/23 = (3·6)/(5·1) = 18/5 = 3 3/5

2) 8 4/5 - 3 3/5 = 5 1/5 = 26/5

3) 26/5 · 12/13 = (2·12)/(5·1) = 24/5 = 4 4/5 = 4,8

№ 2.  1 - 0,15 : (11/12 - 0,75) = 0,1.

1) 11/12 - 0,75 = 11/12 - 3/4 = 11/12 - 9/12 = 2/12 = 1/6

2) 0,15 : 1/6 = 3/20 · 6/1 = (3·3)/(10·1) = 9/10 = 0,9

3) 1 - 0,9 = 0,1

№ 3.  8,3 - (3 5/12 - 1 1/3) : 5/12 = 3,3.

1) 3 5/12 - 1 1/3 = 3 5/12 - 1 4/12 = 2 1/12 = 25/12

2) 25/12 : 5/12 = 25/12 · 12/5 = 25/5 = 5

3) 8,3 - 5 = 3,3

Пошаговое объяснение:

1) 2 1/6 :(8 3/4-5 1/2)=2/3

8 3/4-5 1/2=8 3/4-5 2/4=3 1/4

2 1/6:3 1/4=13/6*4/13=2/3

2)3 17/20:(3 2/5+1 11/15) =3/4

3 2/5+1 11/15=3 6/15+ 1 11/15=4 17/15=

5 2/15

3 17/20:5 2/15=77/20*15/77=3/4

3) (4 3/5-2 1/5):1 1/10 =2 2/11

4 3/5-2 1/5=2 2/5

2 2/5:1 1/10=12/5*10/11=24/11=2 2/11

4)(1 7/10+4/5):1 7/8=1 1/3

1 7/10+4/5=1 7/10+8/10=1 15/10=2 1/2

2 1/2:1 7/8=5/2*8/15=4/3=1 1/3

5) 3 1/8:15/16-1/4

3 1/8:15/16=25/8*16/15=10/3=3 1/3

3 1/3-1/4=3 4/12-3/12=3 1/12

6)1 9/35:(1 1/5+2/3) =33/49

1 1/5+2/3=1 3/15+10/15=1 13/15

1 9/35:1 13/15=44/35*15/28=33/49

7) (11 5/8+7 1/6):3 5/12 =18 19/24

11 5/8+7 1/6=11 15/24+7 4/24=5 1\2

18 19\24:3 5\12=451\24*12\41=11\2=5 1\2

8) (8 7/12-2 5/8):2 1/6=2 3/4

8 7/12-2 5/8=8 14/24-2 15/24=5 23/24

5 23/24:2 1/6=143/24*6/13=11/4=2 3/4