方程式問題(考下各位,解得最好和簡潔為最佳)

x-y=18---(1)---x=18+y---(4)

z+x=19---(2)

y-z=-19---(3)--y=-19+z---(5)

(2),,,,z+x=19
　　z+18+y=19
　　z+18+(-19+z)=19
　　z+18-19+z=19
　　z+z+18-19=19
　　2z-1=19
　　2z=19+1
　　2z=20
　　z=20/2
　　z=10

代,,z=10入,,(5)
y=-19+z
y=-19+10
y=-9

代,,y=-9入,,(4)
x=18+y
x=18+(-9)
x=18-9
x=9

所以x=9,,y=-9,,z=10,

你好！不過是小四數學，有何難呢！


y-z+z+x= 0

y+x= 0

x= -y


x-y=18

-y-y=18

-2y=18

y= -9


x= -y

x= -(-9)

x= 9


y-z= (-19)

-9-z= -19

-z= -10

z= 10

x - y = 18
x = 18 + y ......(1)

y - z = (-19)
z = 19 + y ......(2)

Sub (1) & (2) to z + x = 19

z + x = 19
(19+y) + (18+y) = 19
2y = -18
y = -9

Sub y = -9 into x - y = 18
x - y = 18
x - (-9) = 18
x + 9 =18
x = 9

Sub x = 9 into z + x = 19
z + x = 19
z + 9 = 19
z = 10

Therefore, y = -9, x = 9, z = 10.

希望幫到你...