Question:

The value of the integral, $\int_\limits{1}^{3}\left[ x ^{2}-2 x -2\right] dx ,$ where $[x]$ denotes the greatest integer less than or equal to $x$, is :

Updated On: Feb 14, 2025
  • $-\sqrt{2}-\sqrt{3}+1$
  • $-\sqrt{2}-\sqrt{3}-1$
  • -5
  • -4
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The Correct Option is B

Solution and Explanation

$\int_\limits{1}^{3}\left(\left[(x-1)^{2}\right]-3\right) d x $ $=\int_\limits{1}^{2}\left[x^{2}\right]-3 \int_\limits{1}^{3} d x $ $=\int_\limits{1}^{3} 0 d x+\int_\limits{1}^{\sqrt{2}} 1 .d x+\int_\limits{\sqrt{2}}^{\sqrt{3}} 2.d x+\int_\limits{\sqrt{3}}^{2} 3. d x-6$ $=\sqrt{2}-1+2(\sqrt{3}-\sqrt{2})+3(2-\sqrt{3})-6 $ $=-\sqrt{2}-\sqrt{3}-1$
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Concepts Used:

Integral

The representation of the area of a region under a curve is called to be as integral. The actual value of an integral can be acquired (approximately) by drawing rectangles.

  • The definite integral of a function can be shown as the area of the region bounded by its graph of the given function between two points in the line.
  • The area of a region is found by splitting it into thin vertical rectangles and applying the lower and the upper limits, the area of the region is summarized.
  • An integral of a function over an interval on which the integral is described.

Also, F(x) is known to be a Newton-Leibnitz integral or antiderivative or primitive of a function f(x) on an interval I.

F'(x) = f(x)

For every value of x = I.

Types of Integrals:

Integral calculus helps to resolve two major types of problems:

  1. The problem of getting a function if its derivative is given.
  2. The problem of getting the area bounded by the graph of a function under given situations.