Answer:
• For y-intercept [ x = 0 ]
[tex]{ \rm{y = - 2x - 21}} \\ \\ { \rm{y = ( - 2 \times 0) - 21}} \\ \\ { \rm{y = - 21}} \\ \\ { \boxed{ \rm{ \: y - intercept : \: (0, \: - 21) \: }}}[/tex]
• For x-intercept [ y = 0 ]
[tex]{ \rm{y = - 2x - 21}} \\ \\ { \rm{0 = - 2x - 21}} \\ \\ { \rm{2x = - 21}} \\ \\ { \rm{x = - 10.5}} \\ \\ { \boxed{ \rm{x -intercept : \: ( - 10.5, \: 0) \: }}}[/tex]