Question

Write an explicit formula for an, the nth term of the sequence 7, -28, 112, ....

Answer 1

t( 1 ) = 7

q = t( 2 ) ÷ t( 1 ) = - 28 ÷ 7 = - 4

____________________________

t( n ) = t( 1 ) × q^( n - 1 )

t( n ) = 7 × ( - 4 )^( n - 1 )