Intersecting Curves

Algebra Level 3

The number of points of intersection of the graphs of y = x 2 y=x^2 and y = 1 1 + x 2 y = \dfrac{1}{1+x^2} is

3 4 0 2 1

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1 solution

Ben Habeahan
Sep 4, 2015

The Range of function x 2 0 x^2 \geq 0 and it continius function.

The value of lim x ± 1 1 + x 2 = 1 , \lim_{x \rightarrow \pm \infty } \frac{1}{1+x^2} =1, it's means the asymtot of function y = 1 1 + x 2 y= \frac{1}{1+x^2} is y = 1 y=1 and have intersection with-y at point ( 0 , 1 ) . (0,1).

So, both functions will intersection if: y = 1 1 + y y 2 + y = 1 y 2 + y 1 = 0 y = 1 + 5 2 y= \frac{1}{1+y} \implies y^2+y=1 \implies y^2+y-1=0 \implies y= \frac{-1 + \sqrt5}{2} (Because y = 1 5 2 < 0 y= \frac{-1 - \sqrt5}{2} < 0 ).

Two points of intersection both functions are ( ± 1 + 5 2 , 1 + 5 2 ) ( \pm { \sqrt {\frac{-1 +\sqrt5}{2}}}, \frac{-1 + \sqrt5}{2} ) .

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