simplify (3r^2+4) (2r-1).-8r^3+6r^2
first simpliify(3r^2+4)(2r-1)=(3r^2+4)(2r)+(3r^2+4)(-1)=(6r^3+8r)+(-3r^2-4)=6r^3+8r-3r^2-4=put back6r^3-3r^2+8r-4-8r^3+6r^2=-2r^3+3r^2+8r-4