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How to find range of a function easilyFind range of x/x^2+1

Saksham , 8 Years ago
Grade 11
anser 1 Answers
Shahid
The easiest way I Know is to equate the given function[f(x)] to “y”.
For Example...... 
x/(x2 + 1 ) = y
i.e. x = y(x2 ) + y
i.e.  y(x2 ) – x + y = 0 
This is a Quadratic Equation in terms of “x” 
 
And as it is understood that “x” is real.... The determinant of this equation must be \geq O.....
Therefore (-1)2 – 4(y)(y)  \geq 0 
1 – 4y2  \geq 0 
Thus 4y2 – 1 \leq 0
y2  \leq (1/4)
Therefore.... y\in (-∞ , -1/2) \cup (1/2 , ∞)
This gives the Range of the given function........  i.e.  (-∞ , -1/2) \cup (1/2 , ∞)
Last Activity: 8 Years ago
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