In this video I present the second derivative test in multivariable calculus, which is used to find local maxima/minima/saddle points of a function. However, unlike the nonsense they usually teach in the books, here I'm presenting a more elegant way with…

0,1,0,1,0,1,... https://www.youtube.com/watch?v=OOzPXSfu_mc 0,0,1,0,0,1,... https://www.youtube.com/watch?v=p2nznXSXZMY repeating sequence, math for fun, bla...

just for fun with my students & viewers, how NOT to add fractions, Faray addition, math for fun, blackpenredpen,

Here's the problem: https://www.youtube.com/watch?v=0qxBpBypHEg , blackpenredpen, math for fun,

Ostrogradsky method, or "Ostrogradski" according to https://www.encyclopediaofmath.org/index.php/Ostrogradski_method ,
integral of 1/(1+x^2)^2,
rare integration technique,
via trig substitution, https://www.youtube.com/watch?v=DmdWIWSH904 ,
integral…

Jian's github: https://github.com/Crolabear/record1/blob/master/steveBoringFraction.txt , multi-step fraction addition problems, my kind of number theory, te...

integral of 1/(1+x^2)^2,
integral of 1/(x^2+1)^2,
integral battle,


math for fun,
blackpenredpen,

Check out more calculus lessons on Brilliant: https://brilliant.org/blackpenredpen/ , first 200 people to sign up will get 20% off.

How to evaluate the limit of (n!/n^)^(1/n) as n approaches infinity. This limit problem will turn into a Riemann sum and…

a story in my calc 2 class,
阿胡 solved a problem that I didn't try hard to solve since 2015.

blackpenredpen,
math for fun,


find a recursive formula of a sequence,
find a recurrent formula of a sequence,
find an explicit formula of a sequence,
calculus…

0,0,0,1,0,0,0,1,... my subscriber's formula, faster & better,
sequence,

0,1,0,1,0,1,... https://www.youtube.com/watch?v=OOzPXSfu_mc
0,0,1,0,0,1,... https://www.youtube.com/watch?v=p2nznXSXZMY
repeating sequence,


math for fun,
blackpenredpen,

Evaluate the limit of x^x^x as x goes to 0+
0^0 goes to 1, https://www.youtube.com/watch?v=hjEwb-zfJFM ,
0^0 goes to e, https://www.youtube.com/watch?v=zyQtN7Zbi-c ,
0^0 goes to 0, https://www.youtube.com/watch?v=Gcl_9KIdpso ,

🔑 If you enjoy my videos…

fake solution, extraneous solution, solve rational equations, creating a rational equation with fake a solution, math for fun, blackpenredpen,

another logic/math puzzle! blackpenredpen, math for fun,

Story with my students, Dear Paul, square root equations, square both side, blackpenredpen, math for fun,

integral of 1/(x*(1+x^2)^2),
integral of 1/((1+x^2)^2),
integral by partial fraction,
integral by trig sub,
partial fraction with repeated quadratic factors,
Partial fraction vs. Trig sub


blackpenredpen,
math for fun,

what is 0 to the 0th power? , Can the 0^0 approach to 0, 0^0 goes to 1, https://www.youtube.com/watch?v=hjEwb-zfJFM , 0^0 goes to e, https://www.youtube.com/...