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How to integrate this => INT (3e^(2x) + 2/(25+x^2) dx?

INT 3e^(2x) + 2/(25+x^2) dx

= 3 e^(2x)/2 + 2 [ (1/5) * arctan (x/5) ] + C

= (3 e^(2x))/2 + [(2 * arctan(x/5) )/ 5 ] + C <====

1 Answer

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  • Anonymous
    1 decade ago
    Favorite Answer

    first Part

    ∫3e^(2x) dx

    u = 2x

    du = 2 dx

    dx = (1/2) du

    ∫3e^(2x) dx = ∫3e^u (1/2) du

    = (3/2) e^u = (3/2) e^(2x)

    Second part

    ∫ 2 dx /(25+x^2)

    x = 5 tan(u)

    dx = 5 sec^2(u) du

    u = arctan(x/5)

    ∫ 2 dx /(25+x^2) = 2∫ 5 sec^2(u) du / (25 + 25 tan^2(u))

    = (2/5)∫ sec^2(u) du / (1 + tan^2(u))

    =(2/5)∫ sec^2(u) du / (sec^2(u))

    = (2/5)∫ du

    = 2u / 5 = (2/5)arctan(x/5)

    Finally

    add the two results together , and don't forget the constant

    (3/2) e^(2x) + (2/5)arctan(x/5) + c

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