Final answer:
The result of multiplying (4b+3)(-3b-5) is -12b^2 - 20b - 15.
Step-by-step explanation:
To find the result of multiplying (4b+3)(-3b-5), we use the distributive property. Multiply the first term of the first expression, 4b, with each term in the second expression, -3b and -5. Then multiply the second term of the first expression, 3, with each term in the second expression. Finally, combine like terms to simplify the expression.
Simplifying further, we get -12b^2 - 20b - 15. Therefore, the correct answer is a) -12b^2 - 20b - 15.