２題數學題THX F.1

1.
4(2b＋5)=13–5(9＋b)

4(2b＋5)=13–5(9＋b)
8b+20=13-45-5b
8b+5b=13-45-20
13b=-52
b=-4

2.
21－4b=11b–[3(10b–7)＋45]

21－4b=11b–[3(10b–7)＋45]
21-4b=11b-(30b-21)+4 5
21-4b=11b-30b+21+45
21-21-45=11b-30b+4b
-45=-15b
15b=45
b= 3

NO.1
4(2b)+4(5)=13－5(9)+5(b)
8b+20=13－45+5b
8b+20－20=13－45+5b－20
8b= －52+5b
8b－5b=－52+5b－5b
3b=－52
3b/3=－52/3
b=－52/3
NO.2
21－4b=11b－[3(10b–7)＋45]
21－4b=11b－[3(10b)–3(7)＋45]
21－4b=11b－(30b－21+45)
21－4b=11b－(30b+24)
21－4b=11b－30b－24
21－4b=－19b－24
21－4b+24=－19b－24+24
45－4b+4b=－19b+4b
45=－15b
－15b=45
－15b/－15=45/－15
b=－3

1.
4(2b＋5)=13–5(9＋b)
8b + 20 = 13 - 45 - 5b
8b + 5b = 13 - 45 - 20
13b = -52
b = -4


2.
21－4b=11b–[3(10b–7)＋45]
21 - 4b = 11b - [30b - 21 + 45]
21 - 4b = 11b - 30b +24
-4b - 11b + 30b = 24 - 21
15b = 3
b = 3/15 = 1/5

2007-10-10 16:23:36 補充：
第2題錯左....2.21－4b=11b–[3(10b–7)＋45]21 - 4b = 11b - [30b - 21 + 45]21 - 4b = 11b - [30b +24]21 - 4b = 11b - 30b -24-4b - 11b + 30b = -24 - 2115b = -45b = -3

1)) 4(2b＋5)=13–5(9＋b)
8b+20=13-45-5b
8b+5b=13-45-20
13b=-52
b=-4

2)) 21－4b=11b–[3(10b–7)＋45]
21-4b=11b-(30b-21)+45
21-4b=11b-30b+21+45
21-21-45=11b-30b+4b
-45=-23b
23b=45
b=45/23

no.1

8b+20=72+8b
8b+8b=20+72
16b=92
no.2

21-4b=11b-(30b-21+45)
21-4b=11b-30b+24
21-4b=-19b+24
-23b=45

1.4(2b＋5)=135(9＋b)
8b+5=13-45+5b
8b+5=–32+5b
3b=-37
b=-12 1/3
2.21－4b=11b–[3(10b–7)＋45]
21-4b=11b-(30b-7+45)
21-4b=-19b-38
59=23b
b=2 13/23

1.
4(2b＋5)=13–5(9＋b)
8b+20=13-45-5b
8b+5b=13-45-20
13b=-52
b=-4

2.
21－4b=11b–[3(10b–7)＋45]
21-4b=11b-(30b-21)+45
21-4b=11b-30b+21+45
21-21-45=11b-30b+4b
-45=-23b
23b=45
b=45/23