Question

x^2-  2xy - 4z^2 +y^2taij x=6,y=-4,z=45

Answer 1

\(=\left(x-y\right)^2-4z^2=\left(x-y-2z\right)\left(x-y+2z\right)=\left(6-\left(-4\right)+2.45\right)\left(6-\left(-4\right)-2.45\right)\\ =100.\left(-80\right)=-8000\)

Answer 2

\(=6^2-2\cdot6\cdot\left(-4\right)-4\cdot45^2+\left(-4\right)^2\)

\(=36+16+48-180\cdot45=-8000\)