Simplify (-15xy^4)(-1/3xy^3)

$(- 15 x y^{4}) (- \frac{1}{3} x y^{3})$

Multiply $x$ by $x$ by adding the exponents.

Move $x$ .

$- 15 (x \cdot x) y^{4} (- \frac{1}{3} \cdot (y^{3}))$

Multiply $x$ by $x$ .

$- 15 x^{2} y^{4} (- \frac{1}{3} \cdot (y^{3}))$

Multiply $y^{4}$ by $y^{3}$ by adding the exponents.

Move $y^{3}$ .

$- 15 x^{2} (y^{3} y^{4}) (- \frac{1}{3})$

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$- 15 x^{2} y^{3 + 4} (- \frac{1}{3})$

Add $3$ and $4$ .

$- 15 x^{2} y^{7} (- \frac{1}{3})$

Cancel the common factor of $3$ .

Move the leading negative in $- \frac{1}{3}$ into the numerator.

$- 15 x^{2} y^{7} \frac{- 1}{3}$

Factor $3$ out of $- 15 x^{2} y^{7}$ .

$3 (- 5 x^{2} y^{7}) \frac{- 1}{3}$

Cancel the common factor.

$3 (- 5 x^{2} y^{7}) \frac{- 1}{3}$

Rewrite the expression.

$- 5 x^{2} y^{7} \cdot - 1$

Multiply $- 1$ by $- 5$ .

$5 x^{2} y^{7}$