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中二數學(~急~)
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1.{y=-7x {4x=50+3y From (1) -- y = -7x Putting the y = -7x into (2) 4x = 50 + 3(-7x) 4x = 50 - 21x 25x = 50 x =2 Putting x = 2 into (1) y = -7(2) y = -14 Therefore, x= 2 , y= -14 2.{v=二分之三u ｛u=45-v From (1) -- v =2u/3 Putting v = 2u/3 into (2) u = 45 - 2u/3 u + 2u/ 3 = 45 5u/3 = 45 u =27 Putting u = 27 into (2) 27 = 45- v v =18 Therefore, v = 18, u = 27. 3.{y=2x+25 {4x+3y-5=0 From (1) -- y = 2x +25 Putting y = 2x + 25 into (2) 4x + 3(2x + 25) - 5 = 0 4x + 6x + 75 - 5 =0 10x = -70 x = -7 Putting x = -7 into (1) y = 2(-7) +25 y = -14+ 25 y =11 Therefore, x = -7, y =11 4.p=q+7=49-q {p = q+7 {p = 49 -q From (1) -- p = q+7 Putting p = q+7into (2) q +7 = 49 - q 2q = 42 q =21 Putting q =21 into (1) p = 21 +7 p= 28 Therefore, p = 28, q= 21 5.{2p-3q=5 {3p-3q=8 (1) - (2) = -p = -3 p = 3 Putting p = 3 into (1) 2(3) - 3q = 5 -3q = -1 q =1/3 Therefore, p = 3, q = 1/3 6.{4m-n-5=0 {3m+n-9=0 (1) + (2) = 7m -14 = 0 7m = 14 m = 2 Putting m = 2 into (2) 3(2) + n - 9= 0 -3 + n = 0 n = 3 Therefore, m = 2 , n=3 7.{4x- 二分之三y=6 {2x+ 二分之三y=6 (1) + (2) -- 6x = 12 x =2 Putting x =2 into (1) 4(2) - 2y /3 = 6 -2y/3 = -2 -2y = -6 y =3 Therefore, x = 2, y=3 8.5x-11y+5=5x+2y-60=0 {5x -11y + 5 = 5x+2y-60 {5x-11y+5=0 From (1) -- 5x -11y + 5 = 5x+2y-60 -13y = -65 y = 5 Putting y = 5 into (2) 5x-11(5)+5=0 5x - 55 + 5 = 0 5x = 50 x =10 Therefore, x = 10, y = 5
其他解答:
Excellent!!!
中二數學(~急~)
發問:
此文章來自奇摩知識+如有不便請留言告知
二元一次方程 用代入法 1.{y=-7x {4x==50+3y 2.{v=二分之三u ｛u=45-v 3.{y=2x+25 {4x+3y-5=0 4.p=q+7=49-q 用加減法 5.{2p-3q=5 {3p-3q=8 6.{4m-n-5=0 {3m+n-9=0 7.{4x-二分之三y=6 {2x＋二分之三y=6 8.5x-11y+5=5x+2y-60=0 備註:第二同第七題二分之三即係 3 2最佳解答:
1.{y=-7x {4x=50+3y From (1) -- y = -7x Putting the y = -7x into (2) 4x = 50 + 3(-7x) 4x = 50 - 21x 25x = 50 x =2 Putting x = 2 into (1) y = -7(2) y = -14 Therefore, x= 2 , y= -14 2.{v=二分之三u ｛u=45-v From (1) -- v =2u/3 Putting v = 2u/3 into (2) u = 45 - 2u/3 u + 2u/ 3 = 45 5u/3 = 45 u =27 Putting u = 27 into (2) 27 = 45- v v =18 Therefore, v = 18, u = 27. 3.{y=2x+25 {4x+3y-5=0 From (1) -- y = 2x +25 Putting y = 2x + 25 into (2) 4x + 3(2x + 25) - 5 = 0 4x + 6x + 75 - 5 =0 10x = -70 x = -7 Putting x = -7 into (1) y = 2(-7) +25 y = -14+ 25 y =11 Therefore, x = -7, y =11 4.p=q+7=49-q {p = q+7 {p = 49 -q From (1) -- p = q+7 Putting p = q+7into (2) q +7 = 49 - q 2q = 42 q =21 Putting q =21 into (1) p = 21 +7 p= 28 Therefore, p = 28, q= 21 5.{2p-3q=5 {3p-3q=8 (1) - (2) = -p = -3 p = 3 Putting p = 3 into (1) 2(3) - 3q = 5 -3q = -1 q =1/3 Therefore, p = 3, q = 1/3 6.{4m-n-5=0 {3m+n-9=0 (1) + (2) = 7m -14 = 0 7m = 14 m = 2 Putting m = 2 into (2) 3(2) + n - 9= 0 -3 + n = 0 n = 3 Therefore, m = 2 , n=3 7.{4x- 二分之三y=6 {2x+ 二分之三y=6 (1) + (2) -- 6x = 12 x =2 Putting x =2 into (1) 4(2) - 2y /3 = 6 -2y/3 = -2 -2y = -6 y =3 Therefore, x = 2, y=3 8.5x-11y+5=5x+2y-60=0 {5x -11y + 5 = 5x+2y-60 {5x-11y+5=0 From (1) -- 5x -11y + 5 = 5x+2y-60 -13y = -65 y = 5 Putting y = 5 into (2) 5x-11(5)+5=0 5x - 55 + 5 = 0 5x = 50 x =10 Therefore, x = 10, y = 5
其他解答:
Excellent!!!
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