A380123

完全搞唔掂呀!!??? :Q 試過好多methods都唔work:Q  
求各位大佬打救

題目:
https://1drv.ms/u/s!Ag5XE5B-Qr15geVADWgKMDNjk5mmyw

ym5c2324

is the ans 7/2 ?

A380123

The  answer is 4

A380123

Thank you for your help. However , the answer is 4  Please help solve this sum. Thank you very much.

A380123

Oh my friend, I forgot the instructions of the game.
Therefore, your answer is correct (where the answer provided is 0004, that's why haha)
Would you mind to share the steps of calculation?

A380123

The instructions:

作答時，每題的答案均須以 0 至 9999 之間的整數表示，小於 1000 的答案均須補
「0」以湊足四位數字。如某題的正確答案並非 0 至 9999 之間的整數，應以上述範
圍內最接近正確答案的整數回答。如有兩個整數與正確答案同樣接近，則以「四捨
五入」的原則取較大的整數。例如：
5
 正確答案為 39 時，回答「0039」
 正確答案為 39.2 時，回答「0039」
 正確答案為 39.5 時，回答「0040」
 正確答案為 39.8 時，回答「0040」
 正確答案為 –39 時，回答「0000」
 正確答案為 39000 時，回答「9999」

:lol :lol :lol :lol :lol :lol :lol

mah71512

Add the first 3 equations up to get x^2 + y^2 + z^2 + 2 (x + y + z) = 14/9
Substitute the last equation into the above equation to get (x + y + z)^2 = 0
The rest is pretty obvious.

ym5c2324

我方法唔知會唔會太複雜，我計到 (x + y + z)^2 = 0.

Let z = -x - y,
之後sub去equation 1, 變左條QUADRATIC EQUATION, x= 2 or x = -1.
Sub去EQUATION 2, 變y=2/3 or y = 1/3.

將x同y 4個答案sub去equation3 to prove, 只有 x = -1 and y=2/3 先 PROVE到.
In this case, z=1/3.

Thus, the required answer is 3.5, i.e. 4

A380123

Thanks for your help. You saved my life HAHAHAH

A380123

Very detailed solution, with zillions of thanks!!!!!

kenlam7

Thank you for sharing.