Final answer:
The leading coefficient of the polynomial -15 - 9y + y^4 + 10y is 1, and the degree of this polynomial is 4.
Step-by-step explanation:
The leading coefficient of a polynomial is the coefficient of the term with the highest power. To find this, we arrange the terms of the polynomial in descending order of their exponents. Given the polynomial -15 - 9y + y^4 + 10y, when arranged in descending order of exponents, we have y^4 - 9y + 10y - 15. Simplifying this, we get y^4 + y - 15. The term with the highest power is y^4, which means the leading coefficient is the coefficient of y^4, which is 1 (since any term without a written coefficient has an implied coefficient of 1). The degree of the polynomial is the highest power of the variable y, which in this case is 4 (from the term y^4).