各位高手幫幫忙, 請詳解, 因為看不太懂~

grenuisx

拜託各位高手詳解, 因為小弟我數學真的不濟....
The positive square root of positive number w is multiplied by 4. If this product minus the number w equals 4, what is the value of w?

a)1
b)4
c)9
d)16
e)25


An employee is paid a salary of S dollars by the formula S=c^2-5c, where c is the number of computers she sold. How many computers must she sell in order for her to have a salary of exactly $750?

a)40
b)35
c)30
d)25
e)20

If the sum of a series of consecutive intergers from 1 to n is 190, what is the value of n?

a)11
b)15
c)19
d)23
e)27

The length of a certain rectangle is three times the width of the rectangle. If the number of the square units of its area is 16 more than the number of the linear units of its perimeter, what is the number of the square units of its area?

a)54
b)48
c)42
d)36
e)32


thanks.....

grenuisx

還有一題不知為何這樣解, 搞不懂解法.

Each team in a certain competition played exactly one game with each of the other teams. If there was a total of 28 games played in the competition, what is the number of teams in the competition

a)6     b)7     c)8       d)9      e)10

解題: T*(T-1)/2=28      為何這樣解, 搞不懂為何要.....


thanks..

donna

D  题目有点问题,仅根据The positive square root of positive number w is multiplied by 4这句话,W的正平方根是四的倍数,只有16了.可是this product minus the number w equals 4这句话就不明白了?

C  S=c^2-5c=750    C(C-5)=30*25

C  (N+1)*N=190=20*19

B  设宽为X,则长为3X,那么X*3X=2(X+4X)+16  则X=4 面积为48

donna

以下是引用grenuisx在2003-7-11 15:00:00的发言：
還有一題不知為何這樣解, 搞不懂解法.

Each team in a certain competition played exactly one game with each of the other teams. If there was a total of 28 games played in the competition, what is the number of teams in the competition

a)6     b)7     c)8       d)9      e)10

解題: T*(T-1)/2=28      為何這樣解, 搞不懂為何要.....


thanks..

设队伍数为T,那么C(T,2)=28  也就是T*(T-1)/2=28   T=8

tocean0222

1、由题意：
4*根号w-w=4,得根号w=w,所以w=1
2、就是解方程：c^2-5c=750
得 c=30
3、用等差数列求和公式：
s=n*a1+n(n-1)d/2
得n^2+n-380=0, n=20
4、设width=x
由题意 3x^2-8x-16=0,x=4
则 squre得面积=4*12=48
5、根据题意，2队比赛的可能数等于从队伍中任选2只队
所以 C(n,2)=28,即 n*（n-1）/2=28
得 n=8

grenuisx

thankssss

donna

tocean GG是对的,我把is multiplied by 4看成是4的倍数了,应该是与4相乘.

perfection

以下是引用tocean0222在2003-7-11 16:26:00的发言：
1、由题意：
4*根号w-w=4,得根号w=w,所以w=1

解出w=4.

4*根号w=8.

donna

以下是引用perfection在2003-7-13 13:36:00的发言：

解出w=4.
  
4*根号w=8.

agree