## JozelynW one year ago If the question says insert x=-5 into the equation 4^-x how would you do that? Would you say that 2 negatives equal a positive or just input -5

1. jim_thompson5910

you would replace x with -5 so 4^(-x) = 4^(-(-5)) the two negatives cancel to form a positive which is why 4^(-(-5)) = 4^5

2. anonymous

yeah, it equal to positive

3. JozelynW

ok thank you i was just confused

4. JozelynW

what if its a positive number then?

5. JozelynW

@jim_thompson5910

6. jim_thompson5910

like if x = 9 ?

7. jim_thompson5910

if x = 9, then, $\LARGE 4^{-x} = 4^{-9} = \frac{1}{4^9}$

8. JozelynW

ok

9. JozelynW

what if x=1

10. jim_thompson5910

the negative exponent tells us to take the reciprocal of the base to make the exponent positive $\LARGE x^{-k} = \frac{1}{x^k}$

11. JozelynW

so for 2^x+3 what would x=3 be then

12. jim_thompson5910

$\Large 2^x+3$ or $\Large 2^{x+3}$ ??

13. JozelynW

the second 1

14. JozelynW

i think the answer would be 64

15. jim_thompson5910

$\Large 2^{x+3} = 2^{3+3} = 2^6 = 64$ I agree

16. JozelynW

Ok thanks so much, I'm going to need more help later thou.