Show That If $Y = a X + b ( a \neq 0 ) \text {, then } \operatorname { Corr } ( X , Y ) = + 1 \text { or } - 1$

Essay

Show that if $Y = a X + b ( a \neq 0 ) \text {, then } \operatorname { Corr } ( X , Y ) = + 1 \text { or } - 1$ Under what conditions will $\rho = + 1 ?$