Bài 3
\(a,3x^3y^2-2x^3y^2-7x^3y^2=\left(3-2-7\right)x^3y^2\\ =-6x^3y^2\)
\(b,6x^5y^4z-13x^5y^4z+7x^5y^4z\\ =\left(6-13+7\right)x^5y^4z=0\)
Bài 4
\(a,M=5x^6y+\dfrac{1}{3}x^4y^3-y^7-4x^4y^3+10-5x^6y+2y^7-2,5\\ =\left(5x^6y-5x^6y\right)+\left(\dfrac{1}{3}x^4y^3-4x^4y^3\right)+\left(-y^7+2y^7\right)+\left(10-2,5\right)\\ =-\dfrac{11}{3}x^4y^3+y^7+7,5\)
Bậc của đa thức \(:7\)
b, Thay \(x=-1;y=1\)
\(-\dfrac{11}{3}\times\left(-1\right)^4.1^3+1^7+7,5=\dfrac{29}{6}\)


