Thursday

November 27, 2014

November 27, 2014

Posted by **Paul** on Friday, August 10, 2012 at 2:02pm.

integral at a = -1, b=2

-4dx/(9x^2+30x+25)

Would I have to separate them in 3 terms as:

-4 ∫1/9x^2 + ∫1/30x + ∫1/25

resulting in: -4/(3x^3)+ (15x^2)+ C?

and from there I can replace a and b

f(a) - f(b)?

Thank you

- Calculus -
**Steve**, Friday, August 10, 2012 at 4:27pmBooo!

1/(a+b+c) is NOT 1/a + 1/b + 1/c

What you need to do is let

u = 3x+5 and you have

du = 3 dx, so dx = du/3

x in [-1,2] means u in [2,11]

giving you

∫[2,11] -4/u^2 du/3

-4/3 ∫[2,11] u^-2 du

That should be ever so simple.

- Calculus -
**Paul**, Friday, August 10, 2012 at 6:23pmTHanks Steve, but why 3x+5??

- Calculus -
**Steve**, Saturday, August 11, 2012 at 5:54ambecause you have 9x^2 + 30x + 25 = (3x+5)^2

**Answer this Question**

**Related Questions**

COLLEGE CALCULUS. HELP! - Evaluate the definite integral ∫(0,2) (x-1)^25 ...

Calculus 2 correction - I just wanted to see if my answer if correct the ...

Calculus - Evaluate the triple integral ∫∫∫_E (x+y)dV where E ...

Calculus - Evaluate the triple integral ∫∫∫_E (x)dV where E is...

Calculus - Evaluate the triple integral ∫∫∫_E (xy)dV where E ...

Calculus - Evaluate the triple integral ∫∫∫_E (z)dV where E is...

Calculus - Evaluate the triple integral ∫∫∫_E (xyz)dV where E ...

Integral Help - 1.) ∫ (sin x) / (cos^2 x) dx 2.) ∫ (1) / (1+x^2) dx ...

Calculus - Evaluate the triple integral ∫∫∫_E (x^2.e^y)dV ...

calculus I integral - Is this correct? Evaluate 2x∫1 3t(t^2 + 1)^2 dt u= t...