初三二元一次方程实际应用问题,求详细的解答过程及答案,谢谢 求这道二元一次方程组的详细解答过程,最好能写在纸上,谢谢必采...
\u6c4250\u9053\u4e8c\u5143\u4e00\u6b21\u65b9\u7a0b\u7ec4 50\u9053\u4e00\u5143\u4e00\u6b21\u4e0d\u7b49\u5f0f\u7ec4 100\u9053\u6709\u5173\u4e09\u89d2\u5f62\u7684\u51e0\u4f55\u89e3\u7b54\u9898 \u5e26\u8fc7\u7a0b\u53ca\u7b54\u6848\u8c22\u8c221.2x+9y=81
3x+y=34
2.9x+4y=35
8x+3y=30
3.7x+2y=52
7x+4y=62
4.4x+6y=54
9x+2y=87
5.2x+y=7
2x+5y=19
6.x+2y=21
3x+5y=56
7.5x+7y=52
5x+2y=22
8.5x+5y=65
7x+7y=203
9.8x+4y=56
x+4y=21
10.5x+7y=41
5x+8y=44
11.7x+5y=54
3x+4y=38
12.x+8y=15
4x+y=29
13.3x+6y=24
9x+5y=46
14.9x+2y=62
4x+3y=36
15.9x+4y=46
7x+4y=42
16.9x+7y=135
4x+y=41
17.3x+8y=51
x+6y=27
18.9x+3y=99
4x+7y=95
19.9x+2y=38
3x+6y=18
20.5x+5y=45
7x+9y=69
21.8x+2y=28
7x+8y=62
22.x+6y=14
3x+3y=27
23.7x+4y=67
2x+8y=26
24.5x+4y=52
7x+6y=74
25.7x+y=9
4x+6y=16
26.6x+6y=48
6x+3y=42
27.8x+2y=16
7x+y=11
28.4x+9y=77
8x+6y=94
29.6x+8y=68
7x+6y=66
30.2x+2y=22
7x+2y=47
1.2x+9y=81
3x+y=34
2.9x+4y=35
8x+3y=30
3.7x+2y=52
7x+4y=62
4.4x+6y=54
9x+2y=87
5.2x+y=7
2x+5y=19
6.x+2y=21
3x+5y=56
7.5x+7y=52
5x+2y=22
8.5x+5y=65
7x+7y=203
9.8x+4y=56
x+4y=21
10.5x+7y=41
5x+8y=44
11.7x+5y=54
3x+4y=38
12.x+8y=15
4x+y=29
13.3x+6y=24
9x+5y=46
14.9x+2y=62
4x+3y=36
15.9x+4y=46
7x+4y=42
16.9x+7y=135
4x+y=41
17.3x+8y=51
x+6y=27
18.9x+3y=99
4x+7y=95
19.9x+2y=38
3x+6y=18
20.5x+5y=45
7x+9y=69
21.8x+2y=28
7x+8y=62
22.x+6y=14
3x+3y=27
23.7x+4y=67
2x+8y=26
24.5x+4y=52
7x+6y=74
25.7x+y=9
4x+6y=16
26.6x+6y=48
6x+3y=42
27.8x+2y=16
7x+y=11
28.4x+9y=77
8x+6y=94
29.6x+8y=68
7x+6y=66
30.2x+2y=22
7x+2y=47
\u65b9\u7a0b\u7ec4\u7684\u89e3\u662f:
x=\u20131/2\uff0cy =4/3
y=(x−30)[600−10(x−40)]
=−10x2+1300x−30000;
(2)当x=45时,600−10(x−40)=550(件),
y=−10×452+1300×45−30000=8250(元);
(3)当y=10000时,
10000=−10x2+1300x−30000
解得:x1=50,x2=80,
当x=80时,600−10(80−40)=200<300(不合题意舍去)
故销售价应定为:50元;
(4)y=−10x2+1300x−30000=−10(x−65)2+12250,
故当x=65(元),最大利润为12250元。
1.y=[600-10(x-40)](x-30) =-10x^2+1300x-300002.当y=10000时,得x^2-130x+4000=0解得x=50或x=80当x=50时,卖出件数600-10(50-30)=400,符合题意当x=80时,卖出件数600-10(80-30)=100,不符合题意
3.y=-10(x^2-130x+4225-4225)-30000
=-10(x-65)^2+12250
所以当x=65时,利润取得最大值12250
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