數學題!!!方程(答得好好就最佳回答)
回答 (7)
2007-06-09 2:05 am
✔ 最佳答案
Let x be the number of right questions.y be the number of wrong questions.
5x - 4y = 71--------(1)
.
x + y = 25----------(2)
5 x (2) - (1) :
5x + 5y - 5x + 4 y = 125 - 71
9 y = 54
y = 6
So, he gets 6 wrong
2007-06-09 2:22 am
Let x be the number of correct answer and y is the number of wrong answer
Form two equations
5x - 4y = 71 .......... (1)
x + y = 25 ...............(2) → x = 25 - y ..............(3)
Insert (3) into (1)
5 (25 - y) - 4y = 71
125 - 5y - 4y = 71
125 - 9y = 71
-9y = 71 -125
-9y = -54
9y = 54
therefore y = 54 / 9 = 6
小明答錯 6 題
Form two equations
5x - 4y = 71 .......... (1)
x + y = 25 ...............(2) → x = 25 - y ..............(3)
Insert (3) into (1)
5 (25 - y) - 4y = 71
125 - 5y - 4y = 71
125 - 9y = 71
-9y = 71 -125
-9y = -54
9y = 54
therefore y = 54 / 9 = 6
小明答錯 6 題
2007-06-09 2:18 am
Let A be number of correct questions and B be number of incorrect questions
A + B = 25
A = 25 - B
Sub. B into the equation:
5A - 4B = 71
5(25 - B) - 4B = 71
125 - 5B - 4B = 71
125 - 71 = 9B
54 = 9B
B = 6
Therefore, he had 19 correct questions and 6 incorrect questions
A + B = 25
A = 25 - B
Sub. B into the equation:
5A - 4B = 71
5(25 - B) - 4B = 71
125 - 5B - 4B = 71
125 - 71 = 9B
54 = 9B
B = 6
Therefore, he had 19 correct questions and 6 incorrect questions
參考: Me
2007-06-09 2:13 am
設y為他答對的問題數目.
y*5+[(25-y)*-4]=71
5y-100+4y=71
9y=171
y=19
∴他答錯了25-19=6題
y*5+[(25-y)*-4]=71
5y-100+4y=71
9y=171
y=19
∴他答錯了25-19=6題
參考: me!!@v@
2007-06-09 2:10 am
Let X be the number of correct answers
Let Y be the number of wrong answers
Total number of answers=25
X+Y=25
X=25-Y
5X-4Y=71
5(25-Y)-4Y=71
125-5Y-4Y=71
125-71=9Y
54=9Y
Y=6
X=25-Y
X=25-6
X=19
Therefore
Siu ming got 19 questions right and 6 questions wrong. (Answer is 6)
Checking:
5(19)-4(6)=95-24=71 which is same as given by the question
Let Y be the number of wrong answers
Total number of answers=25
X+Y=25
X=25-Y
5X-4Y=71
5(25-Y)-4Y=71
125-5Y-4Y=71
125-71=9Y
54=9Y
Y=6
X=25-Y
X=25-6
X=19
Therefore
Siu ming got 19 questions right and 6 questions wrong. (Answer is 6)
Checking:
5(19)-4(6)=95-24=71 which is same as given by the question
2007-06-09 2:07 am
Let x 佢答對幾多 y be 答錯幾多,
x+y = 25 (1) <<<< 佢總共答左25條
5x-4y=71 (2) <<<<佢既得分 答對5分 答錯扣4分 最後佢有 71 分
用聯立方程計
(1)x5
5x+5y=125 (3)
(3)-(2):
9y=54
y=6 <<佢答錯左6條.......
答岩都有得計 ....
Sub y=6 into (1)
x+6 =25
x=21
答岩左 21條
x+y = 25 (1) <<<< 佢總共答左25條
5x-4y=71 (2) <<<<佢既得分 答對5分 答錯扣4分 最後佢有 71 分
用聯立方程計
(1)x5
5x+5y=125 (3)
(3)-(2):
9y=54
y=6 <<佢答錯左6條.......
答岩都有得計 ....
Sub y=6 into (1)
x+6 =25
x=21
答岩左 21條
2007-06-09 2:04 am
13.5=.=!
我咁計唔知唔知呢!
5*25-71/4
=.=!
我咁計唔知唔知呢!
5*25-71/4
=.=!
收錄日期: 2021-04-23 19:27:59
原文連結 [永久失效]:
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