Answer :

To subtract the given polynomials, we follow these steps:

1. Write down the polynomials in their original form:
[tex]\[ \left(-8 y^2 - 9 y\right) - \left(-8 y^3 + 9 y^2 - 5 y\right) \][/tex]

2. Distribute the negative sign to the second polynomial:
[tex]\[ -8 y^2 - 9 y - (-8 y^3 + 9 y^2 - 5 y) \][/tex]
becomes:
[tex]\[ -8 y^2 - 9 y + 8 y^3 - 9 y^2 + 5 y \][/tex]

3. Combine like terms by grouping the coefficients of the like powers of [tex]\( y \)[/tex]:
[tex]\[ (8 y^3) + (-8 y^2 - 9 y^2) + (-9 y + 5 y) \][/tex]

4. Simplify each group:
- The coefficient of [tex]\( y^3 \)[/tex] is [tex]\( 8 \)[/tex]:
[tex]\[ 8 y^3 \][/tex]
- The coefficient of [tex]\( y^2 \)[/tex] is [tex]\( -8 - 9 \)[/tex]:
[tex]\[ -8 y^2 - 9 y^2 = -17 y^2 \][/tex]
- The coefficient of [tex]\( y \)[/tex] is [tex]\( -9 + 5 \)[/tex]:
[tex]\[ -9 y + 5 y = -4 y \][/tex]

5. Combine these results into the final polynomial:
[tex]\[ 8 y^3 - 17 y^2 - 4 y \][/tex]

Therefore, the result of subtracting the given polynomials is:
[tex]\[ \boxed{8 y^3 - 17 y^2 - 4 y} \][/tex]