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the function f has a continuous derivative. if f(0) = 1, f(2) = 5 and integral from 0 to 2 f(x) dx = 7, what is integral from 0 to 2 x • f’(x) dx?
a. 3
b. 6
c. 10
d. 17


Sagot :

No photo attached, but no need.

We're given that f(0) = 1 and f(2) = 5, and that

[tex]\displaystyle \int_0^2 f(x) \, dx = 7[/tex]

Integrate x f'(x) by parts, with

[tex]u = x \implies du = dx[/tex]

[tex]dv = f'(x) \, dx \implies v = f(x)[/tex]

Then

[tex]\displaystyle \int_0^2 x f'(x) \, dx = uv\bigg|_{x=0}^{x=2} - \int_0^2 v \, du \\\\ = x f(x) \bigg|_{x=0}^{x=2} - \int_0^2 f(x) \, dx[/tex]

Now just plug in everything you know:

[tex]\displaystyle \int_0^2 x f'(x) \, dx = 2f(2) - 0f(0) - \int_0^2 f(x) \, dx = 10 - 0 - 7 = \boxed{3}[/tex]