Answer :
we have the expression
an=-98+(n-1)(-10)
find a78β
so
For n=78
substitute in the expression
a78=98+(78-1)(-10)
a78=98+(77)(-10)
a78=98-770
we have the expression
an=-98+(n-1)(-10)
find a78β
so
For n=78
substitute in the expression
a78=98+(78-1)(-10)
a78=98+(77)(-10)
a78=98-770