計數勁in!!!!
2006-11-19 4:10 am
if a man walks for x hours at a speed of x km/h and (x-1) hours at speed of (x-1) km/h he will travel a total distance of 41 km ,find the value of x????
回答 (3)
2006-11-19 4:17 am
✔ 最佳答案
Here it is:X x X + (X-1)x(X-1)=41
X^2+X^2-2X+1=41
2X^2-2X=40
2(X^2-X)=40
X^2-X=20
X^2-X-20=0
(X+4)(X-5)=0
X=4 or X= -5
There are two values for X. If you have finding the speed, then x should be at 4 km/h.
2006-11-18 20:18:51 補充：
Sorry,,,,if you ARE finding the value for the speed, should use X =4
參考: myself
2006-11-19 4:23 am
x*x+(x-1)*(x-1)=41
x^2+(x-1)^2=41
x^2+[x^2-2x(1)+1^2]=41
x^2+(x^2-2x+1)=41
x^2+x^ -2x+1=41
2x^2-2x+1-41=0
2x^2-2x-40=0
(2x+8)(x-5)=0
x=5 or x= -4(rejected)
So x=5
P.S: hour 冇可能係負數,所以唔係 -4
x^2+(x-1)^2=41
x^2+[x^2-2x(1)+1^2]=41
x^2+(x^2-2x+1)=41
x^2+x^ -2x+1=41
2x^2-2x+1-41=0
2x^2-2x-40=0
(2x+8)(x-5)=0
x=5 or x= -4(rejected)
So x=5
P.S: hour 冇可能係負數,所以唔係 -4
2006-11-19 4:13 am
x*x+(x-1)^2=41
2x^2-2x+1=41
2x^2-2x-40=0
x^2-x-20=0
(x-5)(x+4)=0
x=5 or -4
2x^2-2x+1=41
2x^2-2x-40=0
x^2-x-20=0
(x-5)(x+4)=0
x=5 or -4
收錄日期: 2021-04-12 22:08:26
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20061118000051KK04698