CE MATHS [復制鏈接]

引用第25樓rBB於2010-04-01 20:47發表的“”:
你有冇打錯野? [表情]
好似有d矛盾 [表情]

應該冇喇

引用第30樓朗仔於2010-04-01 21:03發表的“”:
應該冇喇 [表情]

咁真係唔識了

引用第28樓rBB於2010-04-01 20:56發表的“”:
SUB number:
1+a^2+a^4+.....+ a^2n =
when n=1 : 1+a^2 ======>2 terms
.......

仲係唔多明

引用第32樓朗仔於2010-04-01 21:38發表的“”:
仲有唔多明 [表情] [表情] [表情] [表情]

n=1 有2個term
n=2 有3個term
n=10 有11個term

咁咪有個pattern係,當有n=k時,有(k+1)個term
所以一路加到a^2n...n=n,有(n+1)個term

引用第25樓rBB於2010-04-01 20:47發表的“”:
你有冇打錯野? [表情]
好似有d矛盾 [表情]

oh
原來係two equal roots
sorry呀

引用第33樓rBB於2010-04-01 21:41發表的“”:
n=1 有2個term
n=2 有3個term
n=10 有11個term
.......

引用第35樓朗仔於2010-04-01 21:46發表的“”:
[表情]

a既power由0去到2n，即係0,1x2,2x2, ... ,2(n-2),2(n-1),2n
除以2之後，就變左0,1,2, ... ,n-2,n-1,n，咁好明顯有n+1 terms

引用第22樓朗仔於2010-04-01 17:51發表的“”:
ax^2+2bx+c=0 has two equal real roots, which of the following is/ara true?
I. both roots are -b/a
II. a,b,c form a geometric progression
III. a,b,c form an arithmetic progresion
.......

delta = 0
4b^2 - 4ac = 0
b^2 -ac = 0
b^2 = ac

by definition, II is correct

delta =0
roots = -2b\2a = -b/a

我想問兩條 ..

6 men can finish a piece of work in 10days . If y more men are added, the work can be done in 4days. Find y.
A. 8　　B. 9　　C. 10　　D.11

答案 : B


Which of the following is a factor of 2(a-b)^2 - a^2 + b^2 ?
A. a-3b　　B. a-2b　　C. a+b　　D. a+3b

答案 : A



唔知點做呢?

引用第38樓OldSosad於2010-04-04 16:36發表的“”:
我想問兩條 ..
6 men can finish a piece of work in 10days . If y more men are added, the work can be done in 4days. Find y.
A. 8　　B. 9　　C. 10　　D.11
.......

6 個人用左 10 日 : 6x10

(6+y) 個人用左 4 日 : (6+y)x4

.'. 60 = 24 + 4y
　　y = 9

6 men can finish a piece of work in 10days . If y more men are added, the work can be done in 4days. Find y.

6 men can finish a piece of work in 10days
1 men can finish 1/60 of work everyday

60/4 = 15

15-6=9

Which of the following is a factor of 2(a-b)^2 - a^2 + b^2 ?

2(a-b)^2 - a^2 + b^2
=2 (a^2-2ab+b^2)-a^2+b^2
=a^2-4ab+3b^2
=(a-3b)(a-b)

引用第38樓OldSosad於2010-04-04 16:36發表的“”:
我想問兩條 ..
6 men can finish a piece of work in 10days . If y more men are added, the work can be done in 4days. Find y.
A. 8　　B. 9　　C. 10　　D.11
.......

另外果條:

　2(a-b)^2 - a^2 + b^2
=2(a^2 - 2ab + b^2) - a^2 + b^2
=2a^2 - 4ab + 2b^2 - a^2 + b^2
=a^2 - 4ab + 3b^2
=(a-b)(a-3b)

thanks 兩位

頂唔順 d section B