# integral help

#### mindshift

##### New member
me again, i was wondering if somebody could help me solve this integral"

∫√4x^2 - x^4 dx from 0 to 2

#### soroban

##### Elite Member
Hello, mindshift!

√(4x<sup>2</sup> - x<sup>4</sup>) dx ... from 0 to 2
We have: . x(4 - x<sup>2</sup>)<sup>1/2</sup> dx

Then let u = 4 - x<sup>2</sup>

#### mindshift

##### New member
so then it would be -.5∫ xu^1/2 2 dx from 0 to 2. how would that work?

#### tkhunny

##### Moderator
Staff member
Have you been introduced to the substitution method? You seem to be missing a very important piece.

If u = 4-x<sup>2</sup>,
Then du = -2*x*dx.