What is int_0^4 x/(x^2+9)^(1/2) dx40x(x2+9)12dx ?

1 Answer
Feb 15, 2017

int_0^4 x/(x^2+9)^(1/2) dx = 240x(x2+9)12dx=2

Explanation:

Note that:

d/(dx) (x^2 + 9) = 2xddx(x2+9)=2x

So:

int_0^4 x/(x^2+9)^(1/2) dx = int_0^4 1/2(d/(dx)(x^2+9))(x^2+9)^(-1/2) dx40x(x2+9)12dx=4012(ddx(x2+9))(x2+9)12dx

color(white)(int_0^4 x/(x^2+9)^(1/2) dx) = [(x^2+9)^(1/2)]_0^440x(x2+9)12dx=[(x2+9)12]40
color(white)(int_0^4 x/(x^2+9)^(1/2) dx) = (color(blue)(4)^2+9)^(1/2)-(color(blue)(0)^2+9)^(1/2)40x(x2+9)12dx=(42+9)12(02+9)12
color(white)(int_0^4 x/(x^2+9)^(1/2) dx) = (16+9)^(1/2)-(9)^(1/2)40x(x2+9)12dx=(16+9)12(9)12
color(white)(int_0^4 x/(x^2+9)^(1/2) dx) = 5-340x(x2+9)12dx=53
color(white)(int_0^4 x/(x^2+9)^(1/2) dx) = 240x(x2+9)12dx=2