equation systems:
egin{equation}
1 + 2 = 3
1 = 3 - 2
end{equation}
align text
egin{align}
1+2 &= 3
ewline
f(x) &= x^2
g(x) &= frac{1}{x}
F(x) &= int^a_b frac{1}{3}x^3
abla b& = int x^2dx
end{align}
center a formula : $$a abla b = int x^2dx $$ end
paragraph
This formula (f(x) = x^2) is an example.
$
abla b = int x^2dx $