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← JEE Main 2022 · 29 Jul · Shift 2
MathematicsSingle correct+4 / -1Question 5 of 90

JEE Main 2022 · 29 Jul · Shift 2, Mathematics question 5

If [t] denotes the greatest integer ≤ t, then the value of ∫01[2x−∣3x2−5x+2∣+1]dx\displaystyle\int_0^1\left[2x-\left|3x^2-5x+2\right|+1\right]dx is :

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Answer and worked solution

Official answer: A

Inside. ⌊h+1⌋=⌊h⌋+1\lfloor h+1\rfloor=\lfloor h\rfloor+1 with h=2x−∣3x2−5x+2∣h=2x-|3x^2-5x+2|. On [0,23][0,\frac23], h=−3x2+7x−2h=-3x^2+7x-2 rises from −2-2 to 43\frac43; on [23,1][\frac23,1], h=3x2−3x+2h=3x^2-3x+2 rises from 43\frac43 to 2.

Break points. h=−1h=-1 at x1=7−376x_1=\frac{7-\sqrt{37}}6, h=0h=0 at 13\frac13, h=1h=1 at x2=7−136x_2=\frac{7-\sqrt{13}}6.

Integral of ⌊h⌋\lfloor h\rfloor: −2x1−(13−x1)+(1−x2)=37+13−106-2x_1-\left(\frac13-x_1\right)+(1-x_2)=\frac{\sqrt{37}+\sqrt{13}-10}6; adding 1 gives 37+13−46\dfrac{\sqrt{37}+\sqrt{13}-4}6.

(A)