The expression is .

First group the coefficients and variables.

(10x)(4x⁷) = ( 10 · 4)(x · x⁷)

=  (40) (x · x⁷)            (Multiply: 10 · 4 = 40)

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

=  (40)(x^{1 + 7})

=  40x⁸                        (Add exponents: 1 + 7 = 8)

The product of (10x)(4x⁷) is 40x⁸.