Determine whether the linear transformation T:R² → R², where T(x,y)=(x+y,x-y), is one-one, onto, or both or neither.
A linear transformation is one-one if and only if ker(T)={0}\\ \quadLet
\quad\quad\quad\quad\quad\quad\quad \begin{array}{l}{{T(x,y)=\overline{{{0}}}}}\\ {{\therefore\left(x+y,x-y\right)=(0,0)}}\\ {{x+y=0,x-y=0.}}\end{array}Solving these equations,
\\ \quad\quad\quad\quad\quad\quad\quad\quad x=0,\ \ y=0.The solution is trivial; hence, ker(T)={0}.\\ \quad Hence, T is one-one. \\ \quad A linear transformation is onto if R(T)=W.\\ \quad Let \nu=\left(x,y\right) and w=(a,b) be in R², where a and b are the real numbers such that T(V)=W.
\quad\quad\quad\quad\quad\quad\quad \begin{array}{l}{{T\left(x,y\right)=\left(a,b\right)}}\\ {{\because \left(x+y,x-y\right)=\left(a,b\right)}}\\ {\because x+y=a,x-y=b.}\end{array}Solving these equations,
\quad\quad\quad\quad\quad\quad\quad x={\frac{a+b}{2}},\ \ y={\frac{a-b}{2}}.Thus, for every w=(a,b) in R², there exists a \nu=\left({\frac{a+b}{2}},{\frac{a-b}{2}}\right) in R².
\quad Hence, T is onto.