Решить уравнение (580: b-25)•90+490=850

Question

Математика: Решить уравнение (580: b-25)•90+490=850

kate807 · Accepted Answer

1)
1/3х + 1/5х + 1/6х = 21/40
1*10/3*10х + 1*6/5*6х + 1*5/6*5х = 21/40
10/30х + 6/30х + 5/30х = 21/40
21/30х = 21/40
х = 21/40 : 21/30
х = 21/40 * 30/21
х = 21*30/40*21
х = 30/40
х = 3/4
проверка:
1/3 * 3/4 + 1/5 * 3/4 + 1/6 * 3/4 = 21/40
3/12 + 3/20 + 3/24 = 21/40
3*10/12*10 + 3*6/20*6 + 3*5/24*5 = 21/40
30/120 + 18/120 + 15/120 = 21/40
63/120 = 21/40
21/40 = 21/40

2)
1/4х + 1/6х + 1/8х = 39/56
1*6/4*6х + 1*4/6*4х + 1*3/8*3х = 39/56
6/24х + 4/24х + 3/24х = 39/56
13/24х = 39/56
х = 39/56 : 13/24
х = 39/56 * 24/13
х = 39*24/56*13
х = 3*24/56
х = 72/56
х = 72:2/56:2
х = 36/28
х = 36:4/28:4
х = 9/7 или 1 2/7
проверка:
1/4 * 9/7 + 1/6 * 9/7 + 1/8 * 9/7 = 39/56
9/28 + 9/42 + 9/56 = 39/56
9*6/28*6 + 9*4/42*4 + 9*3/56*3 = 39/56
54/168 + 36/168 + 27/168 = 39/56
117/168 = 39/56
39/56 = 39/56

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