Final answer:
To multiply (-4r^3)(-5r^3), multiply the coefficients (-4)(-5) and add the exponents of the common variable 'r' raised to the power of 3. The answer is 20r^6.
Step-by-step explanation:
To multiply (-4r^3)(-5r^3), we need to multiply the coefficients (-4)(-5) and add the exponents of the common variable 'r' which is raised to the power of 3. Multiplying the coefficients gives us 20, and adding the exponents gives us r^6. Therefore, the answer is 20r^6.