First group the coefficients and variables.

(m⁵)(– 4m⁶) = (1 · – 4) (m⁵ · m⁶)

=  ( – 4) (m⁵ · m⁶)            (Multiply:  1 · – 4 = – 4)

Since base is common, apply the product of powers property: a^m · aⁿ = a^{m + n}.

=  ( – 4) (m^{5 + 6})    

=  – 4m¹¹                        (Add exponents: 5 + 6 = 11)

Product of  Product of (m⁵)(– 4m⁶) is – 4m¹¹.