Question

Expand using identity(ies):

$(x - 2y - z)^{2}$
Please answer it fast​

Answer 1

Answer:

${( a+ b+ c)}^{2} = {a}^{2} + {b}^{2} + {c}^{2} + 2ab + 2bc + 2ca \\ {(x - 2y - z)}^{2} = {x}^{2} + ( - 2y)^{2} + {( - z)}^{2} + 2x( - 2y) + 2x( - z) + 2( - 2y)( - z) \\ = {x}^{2} + 4 {y}^{2} + {z}^{2} - 4xy - 2xz + 4yz$