Final answer:
To add the polynomials, we combine the coefficients of the like terms and keep the variable the same. To subtract the polynomials, we change the sign of the second polynomial and add it to the first polynomial.
Step-by-step explanation:
To add and subtract polynomials, we combine like terms. In this case, the polynomial is (-9y²y)+(-6y-1). To add the polynomials, we combine the coefficients of the like terms (y²y and y) and keep the variable the same. So, (-9y²y) + (-6y-1) can be written as -9y³ - 6y - 1. To subtract the polynomials, we change the sign of the second polynomial (-6y-1) and then add it to the first polynomial. So, (-9y²y) - (-6y-1) can be written as -9y³ + 6y + 1.