標題:
求救 : 三題代入法 10 點
發問:
以下兩題麻煩大大請各位大大幫忙 . . . 用代入消元法 . . . 1. 5r+2s=6 3r=8s-1 2. 2p-5q=24 4p+7q=31 以下的就麻煩各位大大用加減消元法做 . . . 1. 7x+3y=5 5x-4y=22
1. 5r+2s=6------------(1) 3r=8s-1-------------(2) (2): r=(8s-1)/ 3--------------(3) put(3) into (1) 5((8s-1)/3) +2s=6 (40s-5)/3+2s=6 (40s-5)/3+6s/3=6 40s-5+6s=6X3 46s-5=18 46s=18+5 46s=23 s=0.5 r=1 2. 2p-5q=24---------(1) 4p+7q=31--------(2) (2): p=(31-7q)/4---------------(3) put (3) into (1) 2((31-7q)/4)-5q=24 (62-14q-20q)/4=24 <---------通分母 62-34q=96 -34q=34 q= -1 p=19/2 1. 7x+3y=5 X5---------(1) 5x-4y=22 X7-------------(2) (1): 35x+15y=25 (2):35x-28y=154 (1)-(2): 43y= -129 Y= -3 x= 2
其他解答:
[代入法] 1. 5r+2s=6 ---------1 3r=8s-1 ---------2 5r+2s=6 r=(8s-1)/3 ----------3 用3式代入1式, 5r+2s=6 (40s-5)/3+2s=6 40s-5+6s=18 46s =23 s =0.5 用s=0.5代入2式, 3r=8s-1 3r=4-1 3r=3 r=1 所以r=1 s=0.5 [代入法] 2. 2p-5q=24 --------1 4p+7q=31 --------2 2p-5q=24 p=(24+5q)/2 ---------3 用3式代入2式, 4p+7q=31 96+20q)/2+7q=31 96+20q+14q=62 34q= -34 q= -1 用q= -1代入1式, 2p-5q=24 2p-(-5)=24 2p+5=24 2p=19 p=9.5 所以 p=9.5 q= -1 [消元法] 1. 7x+3y=5 -------1 5x-4y=22 -------2 1: x4 28x+12y=20 + 2: x3 15x-12y=66 (28x+12y)+(15x-12y)=20+66 43x = 86 x = 2 用x = 2 代入 2式, 5x-4y=22 10-4y=22 -4y=12 y= -3 所以 x = 2 y = -3 希望幫到你^^|||||1) 5r+2s=6----------(1) 3r=8s-1-----------(2) from (2) r=(8s-1)/3 ---------(3) sub (3) into (1) [5(8s-1)]/3+2s=6 (40s-5)/3+2s=6 40s-5+6s=18 46s=23 s=1/2 sub s=1/2 into (2) 3r=8(1/2)-1 3r=4-1 3r=3 r=1 2) 2p-5q=24--------------(1) 4p+7q=31-------------(2) from (1) p=(5q+24)/2 -----------(3) sub (3) into (2) 4[5q+24)/2]-5q=31 2(5q+24)+7q=31 10q+48+7q=31 17q=-17 q= -1 sub q= -1 into (1) 2p-5(-1)=24 2p+5=24 2p=19 p=9.5 3) 7x+3y=5-----------(1) 5x-4y=22 -------------(2) (1)x 4 28x+12y=20 ----------(3) (2)x3 15x-12y=66 -------------(4) (3)+(4) 43x=86 x=2 sub x=2 into (2) 5(2)-4y=22 10-4y=22 4y= -12 y= -3
求救 : 三題代入法 10 點
發問:
以下兩題麻煩大大請各位大大幫忙 . . . 用代入消元法 . . . 1. 5r+2s=6 3r=8s-1 2. 2p-5q=24 4p+7q=31 以下的就麻煩各位大大用加減消元法做 . . . 1. 7x+3y=5 5x-4y=22
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最佳解答:1. 5r+2s=6------------(1) 3r=8s-1-------------(2) (2): r=(8s-1)/ 3--------------(3) put(3) into (1) 5((8s-1)/3) +2s=6 (40s-5)/3+2s=6 (40s-5)/3+6s/3=6 40s-5+6s=6X3 46s-5=18 46s=18+5 46s=23 s=0.5 r=1 2. 2p-5q=24---------(1) 4p+7q=31--------(2) (2): p=(31-7q)/4---------------(3) put (3) into (1) 2((31-7q)/4)-5q=24 (62-14q-20q)/4=24 <---------通分母 62-34q=96 -34q=34 q= -1 p=19/2 1. 7x+3y=5 X5---------(1) 5x-4y=22 X7-------------(2) (1): 35x+15y=25 (2):35x-28y=154 (1)-(2): 43y= -129 Y= -3 x= 2
其他解答:
[代入法] 1. 5r+2s=6 ---------1 3r=8s-1 ---------2 5r+2s=6 r=(8s-1)/3 ----------3 用3式代入1式, 5r+2s=6 (40s-5)/3+2s=6 40s-5+6s=18 46s =23 s =0.5 用s=0.5代入2式, 3r=8s-1 3r=4-1 3r=3 r=1 所以r=1 s=0.5 [代入法] 2. 2p-5q=24 --------1 4p+7q=31 --------2 2p-5q=24 p=(24+5q)/2 ---------3 用3式代入2式, 4p+7q=31 96+20q)/2+7q=31 96+20q+14q=62 34q= -34 q= -1 用q= -1代入1式, 2p-5q=24 2p-(-5)=24 2p+5=24 2p=19 p=9.5 所以 p=9.5 q= -1 [消元法] 1. 7x+3y=5 -------1 5x-4y=22 -------2 1: x4 28x+12y=20 + 2: x3 15x-12y=66 (28x+12y)+(15x-12y)=20+66 43x = 86 x = 2 用x = 2 代入 2式, 5x-4y=22 10-4y=22 -4y=12 y= -3 所以 x = 2 y = -3 希望幫到你^^|||||1) 5r+2s=6----------(1) 3r=8s-1-----------(2) from (2) r=(8s-1)/3 ---------(3) sub (3) into (1) [5(8s-1)]/3+2s=6 (40s-5)/3+2s=6 40s-5+6s=18 46s=23 s=1/2 sub s=1/2 into (2) 3r=8(1/2)-1 3r=4-1 3r=3 r=1 2) 2p-5q=24--------------(1) 4p+7q=31-------------(2) from (1) p=(5q+24)/2 -----------(3) sub (3) into (2) 4[5q+24)/2]-5q=31 2(5q+24)+7q=31 10q+48+7q=31 17q=-17 q= -1 sub q= -1 into (1) 2p-5(-1)=24 2p+5=24 2p=19 p=9.5 3) 7x+3y=5-----------(1) 5x-4y=22 -------------(2) (1)x 4 28x+12y=20 ----------(3) (2)x3 15x-12y=66 -------------(4) (3)+(4) 43x=86 x=2 sub x=2 into (2) 5(2)-4y=22 10-4y=22 4y= -12 y= -3
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