lovecake

Given the graph y = x*2
.  Which of the
following straight lines should be added so
as to solve the equation 5x*2– x – 2 = 0?
A. 5x – y – 2 = 0
B. 5x – y + 2 = 0
C. x + 5y + 2 = 0
D. x – 5y + 2 = 0

10. If the graphs of y = x*2– 3 and y = 4x + c
touch each other at only one point, then c =  
A. –7  
B. –5  
C. 7
D. 12
11. If  10 3x − = x – 2, then x =  
A. –2
B. 2
C. 3
D. –2 or 3

點解-2唔系其中一個答案??




[ 本帖最後由 lovecake 於 2011-6-7 12:18 PM 編輯 ]

lyrics8888

Given the graph y = x*2 .....
From the equation
x^2 = (x+2)/5
so we should add y=(x+2)/5
Ans is
D. x – 5y + 2 = 0

10. If the graphs of y = x*2– 3 and y = 4x + c  ......
x^2-4x-(3+c)=0
discriminant = 16+4(3+c) = 28-4c =0
so c =7
Ans: C. 7

11. If  10 3x − = x – 2, then x =  .....
It seems that there are some typing mistakes, I do not understand the question.

19. Sum of roots = 6+0 = -b/(-2)
so b = 12.
You can also find b by finding the x-coordinate of the vertex.

夏娜醬大好

引用:

原帖由 lovecake 於 2011-6-4 08:07 AM 發表
11. If  10 3x − = x – 2, then x =  
A. –2
B. 2
C. 3
D. –2 or 3
點解-2唔系其中一個答案??

引用:

原帖由 lyrics8888 於 2011-6-4 10:44 AM 發表
11. If  10 3x − = x – 2, then x =  .....
It seems that there are some typing mistakes, I do not understand the question.

回2#:
由"點解-2唔系其中一個答案??"一句, 可知Ans係C
推斷出問題為 10-3x = x-2


回樓主:
10-3x = x-2
12 = 4x
  x = 3