Question #73ed7

2 Answers
Jan 1, 2018

#1/5x^5+8/3x^3+16x+C#

Explanation:

This looks like a u-substitution problem but you actually need to expand and integrate:

Start:
#int(x^2+4)^2dx#

Expand the integrand:
#=int(x^4+8x^2+16)dx#

Reverse the power rule:
#= 1/5x^5+8/3x^3+16x+C#

Jan 1, 2018

# 1/5 x^5 + 8/3 x^3 + 16x + c #

Explanation:

My natural inteinct is using something called #u# substituion, but we can just expand...

#(x^2+4)^2 -= x^4 + 4x^2 + 4x^2 + 16 #

#=> -= x^4 + 8x^2 + 16 #

Now we have # int x^4 + 8x^2 + 16# # dx #

Now we use #int x^n dx = (x^(n+1))/(n+1) + c #

So our integral:

# color(red)(=> 1/5 x^5 + 8/3 x^3 + 16x + c #