5(x+y)+3(x-y)=90 5(x+y)-3(x-y)=30,解二元一次方程组
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5(x+y)+3(x-y)=90 5(x+y)-3(x-y)=30,解二元一次方程组
5(x+y)+3(x-y)=90
8x+2y=90 1式
5(x+y)-3(x-y)=30
2x+8y=30 2式
1式乘以4-2式
解得 x=11 y=1
5(x+y)+3(x-y)=90
5(x+y)-3(x-y)=30,
两个式子相加:10(x+y)=120,x+y=12
两个式子相减:6(x-y)=60,x-y=10
再相加:2x=22,x=11
y=1
x=11 y=1
令a=x+y, b=x-y,
则:
5a+3b=90
5a-3b=30
相加得:10a=120, a=12
相减得:6b=60, b=10
x+y=12
x-y=10
相加得:2x=22, x=11
相减得:2y=2, y=1
因此解为:(11,1)
x=11,y=1
5(x+y)+3(x-y)=90 5(x+y)-3(x-y)=30
两式相减得
6(x-y)=60
x-y=10
两式相加得
10(x+y)=120
x+y=12
得到的两式再相减得
2y=2
y=1
得到两式再相加得
2x=22
x=11
两个方程进行相加相减后得到一个新的方程组:
X+Y=12;X-Y=6;再相加,之后得X=9,Y=3
两式相加 得 10(x+y)=120 所以 x+y =12
两式相减 得 6 (x-y) =60 所以 x-y =10
所以 x= 11 y= 1
两个方程相加:
10(x+y)=120
x+y=12
把x+y=12带入
12*5+3(x-y)=90
3(x-y)=30
x-y=10
解x+y=12 x-y=10
x=11
y=1
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5(x+y)+3(x-y)=90 5(x+y)-3(x-y)=30,解二元一次方程组
x+y=5; x^y+y^x=17
化简:5(x-y)+2(x+y)-3(x-y)
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