Question

Perform the indicated operations and simplify
21r^3-8r^2+3r+2+(-4r^2+5)-(6r^3-r^2-4r)

Answer 1

get rid of parentheses:
21r^3-8r^2+3r+2-4r^2+5-6r^3+r^2+4r
get like terms together (terms with same exponent):
21r^3-6r^3-8r^2-4r^2+r^2+3r+4r+2+5
do the operations assigned with the coefficients of each group of like terms:
15r^3-10r^2+7r+7

and that's your answer