(c-d)²=c²- 2cd + d²
(a-z)(a+z)= a²-z²
d²+2dc+c²= 2d*(d+c)
n²-t²= (n-t)*(n+t)
k²-r²=(k-r)(k+r)
x³+c³=(x+c)(x²-cx+c²)
(t-y)²=t²-2ty+y²
m³+y³=(m+y)(m²-my+y²)
