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Given that y=2^x, find expressions in terms of y for 2^(x+2)

bobbricks

How do I do this question?
Given that y=2^x, find expressions in terms of y for:
1) 2^(x+2)
2) 2^(3-x)

Reply 1

joostan

Original post by bobbricks

How do I do this question?
Given that y=2^x, find expressions in terms of y for:
1) 2^(x+2)
2) 2^(3-x)

Recall that:

a^{x+y}=a^xa^y

and

a^{x-y}=\dfrac{a^x}{a^y}

How does this help? :smile:

Reply 2

BabyMaths

2^{x+2}=2^x \times 2^2=...

2^{3-x}=\frac{2^3}{2^x}=...

Reply 3

bobbricks

Ah...thanks everyone :biggrin:

Reply 4

nathaliya

Hello bob! I know I've kept you waiting for 7 years, but I have finally cracked the code!!!So basically 2^(x 2) can be broken down to (y)x(2^2) which equals to 4y. And part (ii) can be denoted as (2^3)x(-y) which equals to -8y, but you can write it as 8/y for a positive answer.Hope this helps you out, you're probably out of school and doing a job by now though lol! Enjoy!