\(a,A=\dfrac{1}{4}x^2yz^3\left(-6x^5y^4\right)\\ =\left[\dfrac{1}{4}.\left(-6\right)\right]\left(x^2.x^5\right)\left(y.y^4\right).z^3\\ =-\dfrac{3}{2}x^7y^5z^3\)
Hệ số: `-3/2`
Biến:\(x^7y^5z^3\)
Bậc: 15
\(b.B=2x^4y^3-3x^4y^3+\dfrac{1}{2}x^4y^3\\ =\left(2-3+\dfrac{1}{2}\right)x^4y^3\\ =-\dfrac{1}{2}x^4y^3\)
Thay x=-1, y=2 vào B ta có:
\(B=-\dfrac{1}{2}x^4y^3=-\dfrac{1}{2}.\left(-1\right)^4.2^3=-\dfrac{1}{2}.1.8=-4\)