Question

Help ;-;

Answer 1

a) \(A=x^2\left(x-y\right)-2x^3\left(1+y\right)=x^3-x^2y-2x^3-2x^3y=-x^3-x^2y-2x^3y\)

Tại \(x=2;y=-1\) ta có:

\(A=-2^3-2^2.\left(-1\right)-2.2^3.\left(-1\right)=-8+4+16=12\)

b) \(B=3x^2-\left[2x^2-3x\left(x-4\right)\right]=3x^2-2x^2+3x^2-12x=4x^2-12x\)

Tại \(x=-\dfrac{3}{2}\) ta có: 

\(B=4.\left(-\dfrac{3}{2}\right)^2-12.\left(-\dfrac{3}{2}\right)=4.\dfrac{9}{4}+18=27\)