Answer:
-3r³ + 15r⁴ - 6r³t
Explanation:
-3r² · r: When you multiply the r into the r², simply add the exponents with eachother. The stand-alone r has an exponent of 1 (any number/letter that doesn't have an exponent, such as 2x has an exponent of 1). Makes -3r³
-3r² · -5r²: First, the numbers. -3 · -5 = 15. Same thing with the exponents from earlier. r² + r² = r⁴ Makes 15r⁴
-3r² · 2rt: First, the numbers. -3 · 2 = -6. Now, the variables. r² · rt = r³t. If it helps, separate the variables stuck together, like this. r² · r · t = r³t. Makes -6r³t