问题1.以下哪个关系是函数?说明原因。如果它是一个函数,请确定其域和范围。
(i){(2,1),(5,1),(8,1),(11,1),(14,1),(17,1)}
(ii){(2,1),(4,2),(6,3),(8,4),(10,5),(12,6),(14,7)}
(iii){(1、3),(1、5),(2、5)}
解决方案:
(i) {(2, 1), (5, 1), (8, 1), (11, 1), (14, 1), (17, 1)}
Here, each element in domain is having unique/distinct image. So, the given relation is a function.
Domain = {2, 5, 8, 11, 14, 17}
Range of the function = {1}
(ii) {(2, 1), (4, 2), (6, 3), (8, 4), (10, 5), (12, 6), (14, 7)}
Here, each element in domain is having unique/distinct image. So, the given relation is a function.
Domain = {2, 4, 6, 8, 10, 12, 14}
Range of function = {1, 2, 3, 4, 5, 6, 7}
(iii) {(1, 3), (1, 5), (2, 5)}
This relation is not a function since an element 1 corresponds to two elements/images i.e, 3 and 5.
Hence, this relation is not a function.
问题2。找到以下实函数的范围和范围:
(i)f(x)= – | x |
(ii)f(x)=√(9 – x 2 )
解决方案:
(i) Given,
f(x) = –|x|, x ∈ R
We know that, |x| =
x | if x >= 0 |
-x | if x < 0 |
Here f(x) = -x =
-x | x >= 0 |
x | x < 0 |
As f(x) is defined for x ∈ R, the domain of f is R.
It is also seen that the range of f(x) = –|x| is all real numbers except positive real numbers.
Therefore, the range of f is given by (–∞, 0].
(ii) f(x) = √(9 – x2)
As √(9 – x2) is defined for all real numbers that are greater than or equal to –3 and less than or equal to 3, for 9 – x2 ≥ 0.
|x| <=3
So, the domain of f(x) is {x: –3 ≤ x ≤ 3} or Domain of f = [–3, 3].
For any value of x in the range [–3, 3], the value of f(x) will lie between 0 and 3.
Therefore, the range of f(x) is {x: 0 ≤ x ≤ 3} or we can say Range of f = [0, 3].
问题3.函数f由f(x)= 2x – 5定义。记下
(i)f(0),(ii)f(7),(iii)f(-3)
解决方案:
Given, function, f(x) = 2x – 5.
(i) f(0) = 2 × 0 – 5 = 0 – 5 = –5
(ii) f(7) = 2 × 7 – 5 = 14 – 5 = 9
(iii) f(–3) = 2 × (–3) – 5 = – 6 – 5 = –11
问题4.将t摄氏度转换为华氏温度的函数“ t”由t(C)= 9C / 5 + 32定义。
求(i)t(0)(ii)t(28)(iii)t(–10)(iv)当t(C)= 212时的C值
解决方案 :
Here in ques , it is given that :
t(C) = 9C / 5 +32
So, (i) t(0) = 9(0) / 5 + 32
= 0 + 32
= 32
(ii) t(28) = 9(28) / 5 + 32
Taking LCM and solving ,
= ( 252 +160 ) / 5
= 412 / 5
(iii) t(-10) = 9(-10) / 5 + 32
= -18 + 32
= 14
(iv) Here , in this ques we have to find the value of C.
Given that , t(C) = 212,
9C / 5 + 32 = 212
9C / 5 = 180
9C = 180 X 5
C = 100
The value of C is 100.
问题5.找到以下每个功能的范围。
(i)f(x)= 2 – 3x,x∈R,x> 0。
(ii)f(x)= x2 + 2,x是一个实数。
(iii)f(x)= x,x是一个实数。
解决方案:
(i) Given f (x) = 2 – 3x, x ∈ R, x > 0
∵ x > 0 ⇒ -3x < 0 (Multiplying both sides by -3)
⇒ 2 – 3x < 2 + 0 ⇒ f (x) < 2
∴ Hence, The range of f (x) is (-∞ , 2).
(ii) Given f (x) = x2+ 2, x is a real number
We know x2≥ 0 ⇒ x2+ 2 ≥ 0 + 2
⇒ x2 + 2 > 2 ∴ f (x) ≥ 2
∴ Hence, The range of f (x) is [2, ∞).
(iii) Given f (x) = x, x is a real number.
Let y = f (x) = x ⇒ y = x
∴ Range of f (x) = Domain of f (x)
∴ Hence, Range of f (x) is R. (f(x) takes all real values)