a.
\(\left(-8\right).\left(-3\right)^3.\left(125\right)\\ =\left(-2\right)^3.\left(-3\right)^3.5^3\\ =\left[\left(-2\right).\left(-3\right).5\right]^3\)
b.
\(27.\left(-2^3\right).\left(-7\right).\left(49\right)\\ =3^3.\left(-2\right)^3.\left(-7\right).7^2\\ =\left[3.\left(-2\right)\right]^3.\left(-7\right)^{1+2}\\ =\left(-6\right)^3.\left(-7\right)^3\\=\left[\left(-6\right).\left(-7\right)\right]^3\)
Chắc không cần nữa nhỉ? :))