Question

m, 2m, 4m, . . . The first term in the sequence above is m, and each term thereafter is equal to twice the previous term. If m is an integer, which of the following could NOT be the sum of the first four terms of this sequence?

Answer 1

a) -25
b)-15
c)45
d) 75
e)120

Answer 2

The first four terms are
m, 2m, 4m and 8m
Plug in easy numbers for "m" to see what the sum is.
Forexample, if m= 1, the sum is 1 + 2 + 4 + 8 = 15. If m= 2, the sum is 2 + 4 + 8 + 16 = 30. You will see that the sums are always multiples of 15, so answer A is correct since it isn’t a multiple of 15.
so,
m+ 2,m+ 4,m+ 8,m= 15m
so that the sum of the first four terms is always a multiple of 15.

Answer 3

do u understand?

Answer 4

the answer is a

Answer 5

yes ! thank you so much