Integral

Calculus Level 2

0 2 x 1 d x = ? \large \int_0^2 | x-1 | \, dx = \, ?

3 0 -1 1 2

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3 solutions

0 2 x 1 . d x = 0 1 ( x 1 ) . d x + 1 2 ( x 1 ) . d x [ x 2 2 x ] 0 1 + [ x 2 2 x ] 1 2 = ( 1 2 1 0 + 0 ) + ( 4 2 2 1 2 + 1 ) = 1 2 + 0 + 1 2 = 1 . \large \displaystyle \int_0^2 |x-1| .dx = \int_0^1 -(x-1) .dx + \int_1^2 (x-1) .dx\\ \large \displaystyle \implies - \left[ \frac{x^2}{2} - x \right]_0^1 + \left[ \frac{x^2}{2} - x \right]_1^2\\ \large \displaystyle = - \left( \frac{1}{2} - 1 - 0 + 0 \right) + \left( \frac{4}{2} - 2 - \frac{1}{2} + 1 \right)\\ \large \displaystyle = \frac{1}{2} + 0 + \frac{1}{2} = \color{#D61F06}{\boxed{1}}.

Krishna Karthik
Mar 29, 2019

since you know there is no curvature in the function, because it is an absolute value function, you can just plot it and find the area under the function as a triangle

Since A=1 units^2, the value of the integral must be 1.

William Allen
Apr 15, 2019

Let u = x 1 d u = d x u=x-1 \implies du=dx giving 1 1 u d u = [ 1 2 u u ] 1 1 = 1 2 + 1 2 = 1 \int_{-1}^{1}{|u|}du = \left[ \frac{1}{2}u|u| \right ]_{-1}^{1} = \frac{1}{2}+\frac{1}{2}=1

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