barabaraba
幼苗
共回答了22个问题采纳率:95.5% 举报
1.5x - 3y = 1 (1)
-5x + y = 3 (2)
(1)+(2)=>-2y=4 y=-2.
=>-5x-2=3-5x=5 x=-1
=>x=-1,y=-2.
2.4x - 3y = -2 (1)
3x + y = 5 (2)
(1)+(2)*3=>4x-3y+9x+3y=-2+1513x=13 x=1.
=>3+y=5 y=2.
=>x=1,y=2.
3.3y + 2x =12 (1)
7x - 6y =9 (2)
(1)*2+(2)=>6y+4x+7x-6y=24+911x=33 x=3.
=>3y+6=12 y=2.
=>x=3,y=2.
4.假设一个数为x,则另外一个数为4x.则有:
5x=30
x=6.
=>两个数分别为6,24.
5.假设胜了x场,输了y场,则有:
2x+y=21.(1)
x+y=12.(2)
(1)-(2)=>x=9.
=>y=3.
=>该球队胜出,输掉场比赛的数目分别为9,3场.
6.把方程x - 1 = 1/2(y+1)写成 y = ax + b 的形式
2x-2=y+1
y=2x-1
7.利用代入消元法解以下二元一次联立方程.
(在左手边有一个大括号)
5r + 2s =6.(1)
3r = 8s - 1.(2)
(2)式r=(8s-1)/3.(3)
(3)代入(1)
5(8s-1)/3+2s=6
40s/3+2s-5/3=6
46s/3=23/3
s=1/2
r=1
8)
7.2r - 3s = 37.8.(1)
8.1r =-7s + 11.4.(2)
(1)得s=2.4r-12.6
代入(2)
8.1r =88.2-16.8r+ 11.4
24.9r=99.6
r=4
s=-3
1年前
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