\(a)\) \({\left( {x + y} \right)^2}:\left( {x + y} \right)\) \( = (x + y)^{2-1}\)\( = x + y\)
\(b)\) \({\left( {x - y} \right)^5}:{\left( {y - x} \right)^4}\) \( = {\left( {x - y} \right)^5}:{\left( {x - y} \right)^4} \)\(=(x-y)^{5-4}= x - y\)
\(c)\) \({\left( {x - y + z} \right)^4}:{\left( {x - y + z} \right)^3}\) \( = (x - y + z)^{4-3}\) \( = x - y + z\)
