Question

What is the range of the function f(x) = –2|x + 1|?

all real numbers
all real numbers less than or equal to 0
all real numbers less than or equal to 1
all real numbers greater than or equal to 1

Answer 1

B

Explanation:

all real numbers less than or equal to 0

Answer 2

Range
`\rightarrow` all real numbers less than or equal to 0
`\rightarrow` ( - ∞ , 0 ]

Explanation:

For visual understanding a graph of the function is attached with the answer.

• For calculating the range of any modulus function you need to know that if modulus is there across any function then the output will be always positive.

For example: x has a range of ( - ∞ , + ∞ ) but |x| has a range of [ 0 , + ∞ ). Similarly range of |x + 1| is [ 0 , + ∞ ).

• If you multiply the modulus function with a negative sign then the output will always be negative.

For example: Range of |x| is [ 0 , + ∞ ) but range of -|x| is ( - ∞ , 0 ]. Similarly range of -|x + 1| is ( - ∞ , 0 ]

• Range in this case won't be affected on multiplying a positive constant with the modulus function.

Therefore the range of f(x) = -2|x + 1| will be ( - ∞ , 0 ].

(NOTE : [a,b] means all the numbers between 'a' and 'b' including 'a' and 'b'.

(a,b) means all the numbers between 'a' and 'b' excluding 'a' and 'b'.

(a,b] means all the numbers between 'a' and 'b' including only 'b' not 'a'.

[a,b) means all the numbers between 'a' and 'b' including only 'a' not 'b'.

{a,b} means only 'a' and 'b'.

{a,b] or (a,b} doesn't mean anything. )