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Let f and g be continuous functions on \left [ 0,a \right ] such that f(x)=f(a-x)  and g(x)+g(a-x)=4 , then \int_{0}^{a}f(x)g(x)dx  is equal to : 

  • Option 1)

    -3\int_{0}^{a}f(x)dx

     

     

     

  • Option 2)

    2\int_{0}^{a}f(x)dx

  • Option 3)

    \int_{0}^{a}f(x)dx

  • Option 4)

    4\int_{0}^{a}f(x)dx

Answers (1)

best_answer

 

lower and upper limit -

\int_{a}^{b}f\left ( x \right )dx= \left ( F\left ( x \right ) \right )_{a}^{b}

                = F\left ( b \right )-F\left ( a \right )

 

- wherein

Where a is lower and b is upper limit.

I=\int_{0}^{a}f(x)g(x)dx=\int_{0}^{a}f(a-x)g(a-x)dx

Since \int_{a}^{b}f(x)dx=\int_{a}^{b}f(a+b-x)dx

I=\int_{0}^{a}f(x)(4-g(x))dx=4\int_{0}^{a}f(x)dx

I=2\int_{0}^{a}f(x)dx


Option 1)

-3\int_{0}^{a}f(x)dx

 

 

 

Option 2)

2\int_{0}^{a}f(x)dx

Option 3)

\int_{0}^{a}f(x)dx

Option 4)

4\int_{0}^{a}f(x)dx

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