Math is not riddle

guess is not math method.

suppose f(x)=A(x-5)^2+b, is just a little smart. But would not give the solution easily when the given condition was f(8)=0, in place of f(2)=0. Worse, one might guess that f(5)=8, which would give the wrong anwser f(0)=-128/9, as you did. 

The key to the original or my revised problem is that f(5) is unique, because ff(x) has unique root. and then you can choose the value of f(5) between the two roots of f(x).  

when you realise this point, no smart supposition, nor reasonless guess is needed, let alone the stupid calcul.

 

所有跟帖： 

• 回复：Math is not riddle -jinjing- ♀ (273 bytes) () 07/15/2011 postreply 16:03:10

• Why make stupid calcul when -15少- ♂ (815 bytes) () 07/15/2011 postreply 17:33:47

• You totally misunderstanding me, f(x)=a(X-5)^2+b,why b=2? you te -jinjing- ♀ (37 bytes) () 07/15/2011 postreply 18:04:50

• you tell me,please,not 8. -jinjing- ♀ (0 bytes) () 07/15/2011 postreply 18:07:08

• Ms. Kang has explained, her explanation is not as clear as you d -15少- ♂ (461 bytes) () 07/16/2011 postreply 06:30:03

• Why f(8)=0?Cs we use a Thm, It is unknow for most people here. -jinjing- ♀ (493 bytes) () 07/16/2011 postreply 08:19:30

• You like calcul -15少- ♂ (329 bytes) () 07/16/2011 postreply 09:10:20

• 回复：You totally misunderstanding me, f(x)=a(X-5)^2+b,why b=2? you -15少- ♂ (1365 bytes) () 07/16/2011 postreply 06:09:01