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Q32E
Expert-verifiedEvaluate the integral by interpreting it in terms of areas
The value of integral is \({\rm{ - 4}}{\rm{.5}}\)
Consider the following integral:
\(\int\limits_{\rm{0}}^{\rm{9}} {\left( {\frac{{\rm{1}}}{{\rm{3}}}{\rm{x - 2}}} \right){\rm{dx}}} \)
The objective is to interpret the definite integral \(\int\limits_{\rm{0}}^{\rm{9}} {\left( {\frac{{\rm{1}}}{{\rm{3}}}{\rm{x - 2}}} \right){\rm{dx}}} \) is as the area of the region bounded between the function \({\rm{f(x) = }}\frac{{\rm{1}}}{{\rm{3}}}{\rm{x - 2}}\) and the axis over the interval \(\left( {{\rm{0,9}}} \right)\)
The region is as shown below:
The shaded region consists of two triangles.
Region A is a triangle with base length \({\rm{6}}\)and height \({\rm{2}}\)
So, the area of region A is as follow:
\({\rm{A = }}\frac{{\rm{1}}}{{\rm{2}}}{\rm{bh = }}\frac{{\rm{1}}}{{\rm{2}}}{\rm{(6)(2) = 6}}\)
Region B is a triangle with base length \({\rm{3}}\) and height \({\rm{1}}\)
So, the area of the region B is as follow:
\({\rm{B = }}\frac{{\rm{1}}}{{\rm{2}}}{\rm{bh = }}\frac{{\rm{1}}}{{\rm{2}}}{\rm{(3)(1) = 1}}{\rm{.5}}\)
The total integral is the sum of the positive areas above the \({\rm{x}}\)axis and the negative area below the \({\rm{x}}\)axis.
Then,
\(\int\limits_{\rm{0}}^{\rm{9}} {\left( {\frac{{\rm{1}}}{{\rm{3}}}{\rm{x - 2}}} \right){\rm{dx = - A + B}}} {\rm{ = - 6 + 1}}{\rm{.5 = - 4}}{\rm{.5}}\)
Therefore,
The value of the integral is
\({\rm{ - 4}}{\rm{.5}}\)
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