Question

simplify (xy+yz)^2 - 2x^2y^2 z^2 .find the value when x=-1 ,y=-1 and z =2

Answer 1

since

x = - 1. y = - 1. z = 2

( xy + yz )^2 - 2x^2 2y^2 2z^2

= [ ( - 1 )( - 1 ) + ( - 1 )( 2 ) ] - 2 ( - 1 )^2 + 2 ( - 1 )^2 + 2 ( 2 )^2

= ( 1 - 2 )^2 - 2 × 2 × 8

= 1 - 32

= -31

Answer 2

if x=-1
y=-1
z=2
(xy+yz)² - 2x² × 2y² × z²
=[(-1×-1) + (-1×2)]² -2(-1)²× 2(-1)² ×(2)²
=(1+-2)²-2×2×4
= 1 -16
=-15