Respuesta :
an=a1+d(n-1)
an=nth term
a1=first term
d=common difference
7 is first term=a1
the common difference is -2, they increase by -2 each time
an=7-2(n-1)
expand and distribute
an=7-2n+2
an=9-2n
C is answer
an=nth term
a1=first term
d=common difference
7 is first term=a1
the common difference is -2, they increase by -2 each time
an=7-2(n-1)
expand and distribute
an=7-2n+2
an=9-2n
C is answer