PLs find domain and range
Answers
Answer:
Step-by-step explanation:
Question 1 :
For domain,
f(x) must be a positive real number( including 0 ), which means √( 2 - 2x - x^2 ) ≥ 0
= > 2 - 2x - x^2 ≥ 0
= > x^2 + 2x - 2 ≤ 0
= > x^2 + 2x + 1 - 1 - 2 ≤ 0
= > ( x + 1 )^2 - 3 ≤ 0
= > ( x + 1 )^2 ≤ 3
= > - √3 ≤ x + 1 ≤ √3
= > - √3 - 1 ≤ x ≤ √3 - 1
Domain of this function is [ - √3 - 1 , √3 - 1 ].
Let, √( 2 - 2x - x^2 ) = a
= > a^2 = 2 - 2x - x^2
= > x^2 + 2x - 2 + a^2 = 0
= > x^2 + 2x - ( 2 - a^2 ) = 0
Since a will always be a positive real number, discriminant of this quadratic equation will always be greater than 0 or 0. It means :
= > 2^2 + 4( 1 )( 2 - a^2 ) ≥ 0
= > 4 + 4( 2 - a^2 ) ≥ 0
= > 1 + 2 - a^2 ≥ 0
= > 3 - a^2 ≥ 0
= > - a^2 ≥ - 3
= > a^2 ≤ 3
= > - √3 ≤ a ≤ √3
Since a can never be negative { a = a real number under square root }
= > 0 ≤ a ≤ √3
Range of the given function is [ 0 , √3 ].
Question 2 :
i)
For domain, f(x) must be a real number, here, x - l x l will always be a real number.
Thus domain is { R }.
For range,
For every real number, l x l ≥ x
= > l x l - x ≥ 0
= > x - l x l ≤ 0
Range is ( - ∞ , 0 ]
ii)
f(x) will always be a real number, so domain is { R }.
For range,
If x = +ve, l x l + x ≥ 0 { +ve no. + +ve no. = another +ve no. or 0 }
If x = - ve, l x l + x = 0 { - x + x = 0 }
Thus, l x l + x ≥ 0
l x l + x will always be a positive number.
Hence, range is [ 0 , ∞ ).
Answer:
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