Respuesta :

let √ be a square root

3√(5c)×7√(15c²)

1. take out the c² from√

3√(5c)×7c√15

2.multiply the coefficients and √, also use the √ rule of using single√.

21c√(5c×15)

3. and 4. get 25 of the √.

21c√(25×3c)

21×5c√(3c) 

5. multiply the coefficients

105c√(3c)