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JEE Main 202225 JuneEvening Shift
Exam
JEE Main
Year
2022
Date
25 June
Shift
Evening Shift
Subject
Mathematics
Chapter
Continuity and Differentiability

JEE Main 2022 · 25 June · Evening Shift · Mathematics · Continuity and Differentiability

Let f(x) = [2 x ^ 2 + 1] and g(x) = \ cases 2x - 3, & x < 0 2x + 3,...

Let f(x)=[2x2+1]andf\left(x\right) = \left[2{x}^{2} + 1\right] andg\left(x\right) = \left\{{2x−3,x<02x+3,x≥0\begin{cases}2x - 3, & x < 0 \\ 2x + 3, & x \ge 0\end{cases}\right), where [t]isthegreatestinteger\left[t\right] is the greatest integer\le t.Then,intheopeninterval(−1,1). Then, in the open interval \left(- 1, 1\right), the number of points where fog is discontinuous is equal to ______.

Correct answer

0

Step-by-step solution

Given,

ff\left(x\right) = \left[2{x}^{2} + 1\right]andandg\left(x\right) = \left\{{2x−3,x<02x+3,x≥0\begin{cases}2x - 3, & x < 0 \\ 2x + 3, & x \ge 0\end{cases}\right)

Now, f(g(x))=[2g2(x)]+1f\left(g\left(x\right)\right) = \left[2{g}^{2}\left(x\right)\right] + 1

= \left\{[2(2x−3)2]+1;x<0[2(2x+3)2]+1;x≥0\begin{array}{ll}\left[2{\left(2x - 3\right)}^{2}\right] + 1; x < 0 \\ \left[2{\left(2x + 3\right)}^{2}\right] + 1; x \ge 0\end{array}\right)</p><p>Ifx < 0thenthen- 1 < x < 0 ⇒ - 2 < x < 0</p><p></p><p>⇒ - 5 < 2x - 3 < - 3 ⇒ ⇒ 9 < {\left(2x - 3\right)}^{2} < 25</p><p></p><p>⇒ 18 < 2{\left(2x - 3\right)}^{2} < 50,Sotherewillbe, So there will be31valueswherevalues where2{\left(2x - 3\right)}^{2} is integer, Similarly for 2(2x+3)22{\left(2x + 3\right)}^{2} there will be 3131, so total 6262 points of discontinuity

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