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On line solution of multivariate equations：
    First set the elements of the equation (i.e. the number of unknowns), then click the "Next" button to enter the coefficients of each element of the equation set, and click the "Next" button to obtain the solution of the equation set.
    Note that the coefficients of each element of the equation system can only be numbers, not algebraic expressions (including mathematical functions).
    Current location：Equations > Multivariate equations > Answer
detailed information：
The input equation set is:
 40A -20B - 
1
2
D = 0    (1)
-20A + 26B = 0    (2)
 35C + 
1
2
D = 0    (3)
-1B + C = 
7
2
    (4)
Question solving process:

Divide the two sides of equation (1) by 2, the equation can be obtained:
         20A -10B - 
1
4
D = 0    (5)
, then add the two sides of equation (5) to both sides of equation (2), the equations are reduced to:
 40A -20B - 
1
2
D = 0    (1)
 16B - 
1
4
D = 0    (2)
 35C + 
1
2
D = 0    (3)
-1B + C = 
7
2
    (4)

Divide the two sides of equation (2) by 16, the equation can be obtained:
         B - 
1
64
D = 0    (6)
, then add the two sides of equation (6) to both sides of equation (4), the equations are reduced to:
 40A -20B - 
1
2
D = 0    (1)
 16B - 
1
4
D = 0    (2)
 35C + 
1
2
D = 0    (3)
 C - 
1
64
D = 
7
2
    (4)

Divide the two sides of equation (3) by 35, the equation can be obtained:
         C + 
1
70
D = 0    (7)
, then subtract both sides of equation (7) from both sides of equation (4), the equations are reduced to:
 40A -20B - 
1
2
D = 0    (1)
 16B - 
1
4
D = 0    (2)
 35C + 
1
2
D = 0    (3)
- 
67
2240
D = 
7
2
    (4)

Multiply both sides of equation (4) by 1120
Divide both sides of equation (4) by 67, get the equation：
        - 
1
2
D = 
3920
67
    (8)
, then add the two sides of equation (8) to both sides of equation (3), get the equation：
 40A -20B - 
1
2
D = 0    (1)
 16B - 
1
4
D = 0    (2)
 35C = 
3920
67
    (3)
- 
67
2240
D = 
7
2
    (4)

Multiply both sides of equation (4) by 560
Divide both sides of equation (4) by 67, get the equation：
        - 
1
4
D = 
1960
67
    (9)
, then subtract both sides of equation (9) from both sides of equation (2), get the equation：
 40A -20B - 
1
2
D = 0    (1)
 16B = - 
1960
67
    (2)
 35C = 
3920
67
    (3)
- 
67
2240
D = 
7
2
    (4)

Multiply both sides of equation (4) by 1120
Divide both sides of equation (4) by 67, get the equation：
        - 
1
2
D = 
3920
67
    (10)
, then subtract both sides of equation (10) from both sides of equation (1), get the equation：
 40A -20B = - 
3920
67
    (1)
 16B = - 
1960
67
    (2)
 35C = 
3920
67
    (3)
- 
67
2240
D = 
7
2
    (4)

Multiply both sides of equation (2) by 5
Divide both sides of equation (2) by 4, get the equation：
         20B = - 
2450
67
    (11)
, then add the two sides of equation (11) to both sides of equation (1), get the equation：
 40A = - 
6370
67
    (1)
 16B = - 
1960
67
    (2)
 C = 
112
67
    (3)
 D = - 
7840
67
    (4)

The coefficient of the unknown number is reduced to 1, and the equations are reduced to：
 A = - 
637
268
    (1)
 B = - 
245
134
    (2)
 C = 
112
67
    (3)
 D = - 
7840
67
    (4)


Therefore, the solution of the equation set is:
A = - 
637
268
B = - 
245
134
C = 
112
67
D = - 
7840
67


Convert the solution of the equation set to decimals:
A = -2.376866
B = -1.828358
C = 1.671642
D = -117.014925

解方程组的详细方法请参阅：《多元一次方程组的解法》
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