✔ 最佳答案
{ 2a - 7b = 0 -------(1)
{4a - 7b + 10 = 0 -------(2)
(2) - (1)
4a - 7b +10 - ( 2a - 7b ) = 0 - 0
4a - 7b + 10 - 2a + 7b = 0
2a + 10 = 0
a = -5
將 a = -5 代入 (1)
2 (-5) - 7b = 0
-10 - 7b = 0
-7b = 10
b = - ( 10 / 7 )
∴a = -5,b = - ( 10 / 7 )。
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{9p + 4q + 2 = 0 -------(1)
{9p - 2q - 28 = 0 -------(2)
(1) - (2)
9p + 4q + 2 - ( 9p - 2q - 28 ) = 0
9p + 4q + 2 - 9p + 2q + 28 = 0
6q + 30 = 0
q = -5
將 q = -5 代入 (1)
9p + 4(-5) + 2 = 0
9p - 20 + 2 = 0
9p = 18
p = 2
∴p = 2,q = -5。
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{3x + 4y = 2 --------(1)
{6x - 7y = 19 --------(2)
(1) × 2 - (2)
2 ( 3x + 4y ) - ( 6x - 7y ) = 2 × 2 - 19
6x + 8y - 6x + 7y = -15
15y = -15
y = -1
將 y = -1 代入 (1)
3x + 4(-1) = 2
3x - 4 = 2
3x = 6
x = 2
∴x = 2,y = -1。