Question

help

Answer 1

Bài 1 :

a) Ta có :
\(M=x^2\left(x+1\right)-y^2\left(y-1\right)+xy-3xy\left(x-y+1\right)-95\)

\(=x^3+x^2-y^3+y^2+xy-3x^2y+3xy^2-3xy-95\)

\(=\left(x^3-3x^2y+3xy^2-y^3\right)+\left(x^2+y^2-2xy\right)-95\)

\(=\left(x-y\right)^3+\left(x-y\right)^2-95\)

\(=7^3+7^2-95\)

\(=297.\)

b) \(N=3x^2-2x+3y^2-2y+6xy-100\)

\(=\left(3x^2+3y^2+6xy\right)-\left(2x+2y\right)-100\)

\(=3\left(x+y\right)^2-2\left(x+y\right)-100\)

\(=3.25-2.5-100\)

\(=-35.\)