Question

Can anyone help me please ?

Answer 1

3 Answers: Choice B, C, and D

Basically, everything except choice A.

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Explanation:

All exponential functions can be written into the form y = a*b^x

The b term determines if we have growth or decay.

If 0 < b < 1, then we have decay. If b > 1, then we have growth.

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For choice A, we have b = 1.7 which satisfies b > 1. This represents growth. So we cross choice A off the list.

Choice B looks almost identical since it appears b = 1.7 here as well, but note the negative exponent. It might help to rewrite choice B into y = 3( 1.7^(-2) )^x and note how b = (1.7)^(-2) = 0.346 approximately. This represents decay.

Choice C has b = 1/3 = 0.33 approximately which is also decay.

Finally, choice D has b = 2^(-1) = 1/(2^1) = 1/2 = 0.5 which is also decay.

Choices B through D have b values such that 0 < b < 1.

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Check out the graph below. It visually confirms the answers mentioned earlier. A growth function goes uphill as we move to the right, while a decay function moves downhill while moving to the right.

I used GeoGebra to make the graph.