Find the value of integral v3v1(bav)dv?

3 Answers
Jun 20, 2017

v3v1(bav)dv=b(v3v1)a2(v23v21)

= (v3v1)(ba2(v3+v1))

Explanation:

v3v1(bav)dv

= v3v1bdvv3v1avdv

= bv3v1dvav3v1vdv

= b[v]v3v1a[12v2]v3v1

= b(v3v1)a2(v23v21)

or (v3v1)(ba2(v3+v1))

Jun 20, 2017

See explanation.

Explanation:

v3v2(bav)dv=

[bvav22]v=v3v=v2

=bv3(av3)2(bv2(av2)2)=

bv3a2v23bv2+a2v22=

b(v3v2)a2(v23v22)=

b(v3v2)a2(v3v2)(v3+v2)=

(v3v2)(ba2(v3+v2))=

(v3v2)(ba2v3a2v2))

In the first line I used the following properties of integral:

  • (a)dx=ax

  • (xn)dx=xn+1n+1

Jun 20, 2017

(v3v2)(ba2(v3+v2))

Explanation:

When you integrate to expressions subtracted from each other, integrate each item separately.

v3v2bdvv3v2avdv

You can bring the constants of integration out to the front.

bv3v2dvav3v2vdv

Tables of integrals should give you the integration of these two

[bva2v2]v3v2

Evaluate the integral at the two limits of integration

[bv3a2(v3)2][bv2a2(v2)2]

This is really a good stopping point, but you can try to simplify if you like as well.

bv3a2(v3)2bv2+a2(v2)2

bv3bv2a2(v3)2+a2(v2)2

b(v3v2)a2((v3)2(v2)2)

b(v3v2)a2(v3v2)(v3+v2)

(v3v2)(ba2(v3+v2))