How do you solve int_0^1 sqrt(5x+4) dx105x+4dx?

1 Answer
Jan 17, 2017

38/153815

Explanation:

We need to use a u-substitution to solve this question.

STEP 1: Identify the u
u = 5x+4u=5x+4

STEP 2: Find du
du = 5 dxdu=5dx

STEP 3: Change the x-bounds to u-bounds
x = 0 -> u = 5(0)+4 = 4x=0u=5(0)+4=4
x = 1 -> u = 5(1)+4 = 9x=1u=5(1)+4=9

STEP 4: Do the u-substitution
int_0^1 sqrt 5x+4 dx105x+4dx
=int_4^9 sqrt(u) * 1/5 du=94u15du
remember: we found du = 5dxdu=5dx, so if we solve for dxdx we get dx=1/5 dudx=15du
=1/5 int_4^9 sqrt(u) du=1594udu
=1/5 [2/3 u^(3/2)]_4^9=15[23u32]94
=2/15[u^(3/2)]_4^9=215[u32]94
=2/15(3^3 - 2^3)=215(3323)
=2/15(19)=215(19)
=38/15=3815