F.4 Function

👨🏻‍🏫 學術台數學

KelvinLo

2009-12-30 5:18 am

Determine whether y is a function of x for x >= 0

1. y = √ (3x+1)

更新1:

The answer is yes But..... When x = 8 y = √ ( 3(8) + 1) =√ 25 = +5 or = -5 that means one x has 2 values of y so that is not a function am i correct?

更新2:

Why it cannot be -5? -5 x -5 = 25 5 x 5 = 25

回答 (3)

用戶2053

2009-12-30 6:04 am

✔ 最佳答案

y = √ (3x+1)

for x >= 0

√ (3x+1) >= √ [(3(0) + 1]

√ (3x+1) >= 1

y >= 1

2009-12-29 22:21:01 補充：
Your concept is not clear !

For any x , √x is positive.

2009-12-29 22:22:36 補充：
x^2 = 25

x = +√ 25 or - √ 25

2009-12-29 22:23:43 補充：
√ 25 = 5 only

not = - 5

2009-12-29 23:15:59 補充：
You remamber that :

The roots of x^2 = x or - x
;
But the answer of √ x^2 is = |x| only!

For example : √(- 5)^2 = |-5| = 5 only

Hope can help you!!

👍 0 👎 0

[匿名]

2009-12-31 2:59 am

這裏可以幫到你
http://actionte.subo.cn35.com/yahoo.com.hk/hk/auction/178987536

👍 0 👎 0

用戶9112

2009-12-30 7:13 am

√ 係正根咁解.負根要咁樣表示 -√

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