Question

1. a, Cho x-y= 7, tính gt biểu thức

A= x(x+z)+ y(y-z)-2xy+37

b, Cho x+2y =5,tính gt biểu thức

B= x²+4y²-2x+10+4xy-4y

Answer 1

\(a.\)

\(x\left(x+z\right)+y\left(y-z\right)-2xy+37\)

\(=x^2+xz+y^2-yz-2xy+37\)

\(=\left(x^2-2xy+y^2\right)+z\left(x-y\right)+37\)

\(=\left(x-y\right)^2+z\left(x-y\right)+37\)

\(=7^2+x.7^2+37\)

\(=86+49x\)

\(b.\)

\(x^2+4y^2-2x+10+4xy-4y\)

\(=\left(x^2+4xy+4y^2\right)-2\left(x+2y\right)+10\)

\(=\left(x+2y\right)^2-2\left(x+2y\right)+10\)

\(=5^2-2.5+10\)

\(=25\)