Question

Which of the following functions decreases, going downwards from left to right on a graph?

A.y = 4^x - 2
B.y = (1/3) (4)^x
C.y = 2 (1/5)^x
D.y = -3 (1/2)^x

Answer 1

How can i tell ?

Answer 2

general form of exponential function
\[y = a*b^{x}\]
"a" can be either pos or neg .... pos = increasing, neg = decreasing
"b" can be either less than 1 or greater than 1
... less = decreasing , greater = increasing

Answer 3

you can always plot some points to get an idea of what each graph looks like as well

Answer 4

ok so is it A?

Answer 5

Or D?

Answer 6

Ohh its 4 becouse 1/2 is less than 1

Answer 7

A lol not 4

Answer 8

haha i made a mistake, sorry for confusion ignore what i said about "a" above
look at whether "b" is greater or less than 1 , then if "a" is neg just flip your answer

Answer 9

its not answer A because its "4^x" 4>1 so its increasing

Answer 10

ohh would it be D then ?

Answer 11

1/2<1

Answer 12

yes however, the 3 is neg in front of it so that flips the graph making it increasing

Answer 13

soo if a number was positive it would flip negative too?

Answer 14

?? i dont follow
if "a" is negative it reflects the graph vertically, thus switching increasing to decreasing and switching decreasing to increasing