Simplify the expression. (9x^4y^5) (-2x^2y^7)
To simplify the expression (9x^4y^5) (-2x^2y^7), we will combine the like terms and apply the properties of exponents.
Using the product rule of exponents, we multiply the coefficients 9 and -2 to give -18:
-18x^(4+2)y^(5+7) = -18x^6y^12
Therefore, the simplified expression is -18x^6y^12.