`a, 11^3 - 1 = 11^3 - 1^3 = (11-1)(11^2 + 11 + 1) = 10 . 133 = 1330`.
`b, x^3 - y^3 = (x-y)^3 - 3xy(x-y) = 6^3 - 3.9 . 6 = 54`
a)
\(11^3-1=\left(11-1\right)\left(11^2+11+1^2\right)=10\cdot138=1380\)
b)
\(x^3-y^3=\left(x-y\right)^3+3xy\left(x-y\right)=6^3+3\cdot9\cdot6=378\)