∫abxⅆxx2+a2
a+b
a+b¯
x+x+x+x⏞ktimes
a+b→
abcd
-b±b2-4ac2a
(-b±√(b^2-4ac))/2a
a+bn=∑k=0nnkakbn-k
(a+b)^n=∑_(k=0)^n▒(n¦k) a^k b^(n-k)