4-2.Quadratic Equations and Inequations
hard

The equation $x^2-4 x+[x]+3=x[x]$, where $[x]$ denotes the greatest integer function, has:

A

exactly two solutions in $(-\infty, \infty)$

B

no solution

C

a unique solution in $(-\infty, 1)$

D

a unique solution in $(-\infty, \infty)$

(JEE MAIN-2023)

Solution

$x^2-4 x+[x]+3=x[x]$

$\Rightarrow x^2-4 x+3=x[x]-[x]$

$\Rightarrow(x-1)(x-3)=[x] .(x-1)$

$\Rightarrow x=1 \text { or } x-3=[x]$

$\Rightarrow x-[x]=3$

$\Rightarrow\{x\}=3 \text { (Not Possible) }$

Only one solution $x=1$ in $(-\infty, \infty)$

Standard 11
Mathematics

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