fully simplify

14xy^4(-14y)

To fully simplify the expression 14xy^4(-14y), we will combine like terms and perform the multiplication.

We have:
14xy^4(-14y)

Multiplying the coefficients, we get:
14 * (-14) = -196

Multiplying the x terms, we get:
x * y = xy

Multiplying the y terms, we add the exponents:
y^4 * y = y^(4+1) = y^5

Putting it all together, the fully simplified expression is:
-196xy^5