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

Question

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

jim_thompson5910 · Answer

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

anonymous · Answer

yeah, it equal to positive

jozelynw · Answer

ok thank you i was just confused

jozelynw · Answer

what if its a positive number then?

jozelynw · Answer

@jim_thompson5910

jim_thompson5910 · Answer

like if x = 9 ?

jim_thompson5910 · Answer

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

jozelynw · Answer

ok

jozelynw · Answer

what if x=1

jim_thompson5910 · Answer

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

jozelynw · Answer

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

jim_thompson5910 · Answer

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

jozelynw · Answer

the second 1

jozelynw · Answer

i think the answer would be 64

jim_thompson5910 · Answer

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

jozelynw · Answer

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