x+y=20000①3%x+1.5%y=525②的解二元一次方程2.a+b=2300/1+15%①(1+25%)a+(1-25%)b=2300②3.x-y=50①x(1+15%)-y(1-15%)=95②4x-y=500①x(1+15%)+y(1-10%)=950②5.x/50=y+2/5①x/75=y-2/5②6.x+y=8000①0.9%x+2.2%y=137②

Question

x+y=20000 ①3%x+1.5%y=525②的解二元一次方程
2.a+b=2300/1+15%①
(1+25%)a+(1-25%)b=2300②
3.x-y=50①
x(1+15%)-y(1-15%)=95②
4 x-y=500①
x(1+15%)+y(1-10%)=950②
5.x/50=y+2/5①
x/75=y-2/5②
6.x+y=8000①
0.9%x+2.2%y=137②

Answer 1

x+y=20000 ①3%x+1.5%y=525②
(1)*0.03-(2)
0.03x+0.03y-0.03x-0.015y=20000*0.03-525
0.015y=75
y=5000
x=20000-y=15000
a+b=2300/1+15%①
(1+25%)a+(1-25%)b=2300②
(1)*1.25-(2)
1.25a+1.25b-1.25a-0.75b=2000*1.25-2300
0.5b=200
b=400
a=2000-b=1600
x-y=50①
x(1+15%)-y(1-15%)=95②
(1)*1.15-(2)
1.15x-1.15y-1.15x+0.85y=50*1.15-95
-0.3y=-37.5
y=125
x=y+50=175
x-y=500①
x(1+15%)+y(1-10%)=950②
(1)*1.15-(2)
1.15x-1.15y-1.15x+0.9y=500*1.15-950
-0.25y=-375
y=1500
x=y+500=2000
x/50=(y+2)/5①
x/75=(y-2)/5②
(1)-(2)
x*(1/50-1/75)=(y+2-y+2)/5
x/150=4/5
x=120
代入(1),120/50=(y+2)/5
y+2=12
y=10
x+y=8000①
0.9%x+2.2%y=137
(1)*0.009-(2)
0.009x+0.009y-0009x-0.022y=8000*0.009-137
-0.013y=-65
y=5000
x=8000-y=3000