Question

1. (r² + 3r⁴ - 6r³) - (4r² + 2r⁴ - 7r³)

Explanation:

Step1: Remove parentheses

$(r^{2}+3r^{4}-6r^{3})-(4r^{2}+2r^{4}-7r^{3})=r^{2}+3r^{4}-6r^{3}-4r^{2}-2r^{4}+7r^{3}$

Step2: Combine like - terms

For the $r^{2}$ terms: $r^{2}-4r^{2}=-3r^{2}$; for the $r^{4}$ terms: $3r^{4}-2r^{4}=r^{4}$; for the $r^{3}$ terms: $-6r^{3}+7r^{3}=r^{3}$
So the result is $r^{4}+r^{3}-3r^{2}$

Answer:

$r^{4}+r^{3}-3r^{2}$