Question

help evaluate

80*2^-0/28=
80*2^28/28=
80*2^56/28=

Answer 1

\[\LARGE 80*\left(2\right)^{-0/28}=\] is this what you mean?

Answer 2

yup

Answer 3

i got 160

Answer 4

\[\LARGE \frac0b=0\] any number instead of b \[\Large b\neq0\] is equal to 0

so you have ...?

Answer 5

80

Answer 6

\[\LARGE x^{-a}=\frac{1}{x^a}\]

Answer 7

i really dnt get this...

Answer 8

example?

Answer 9

\[\LARGE 80\cdot \left(2\right)^{\frac{-0}{28}}=80\cdot 2^0=80\cdot 1\]

Answer 10

oooh i got the steps right but instead i did 80*2 then i did 0 which gave me 160 thnks @Kreshnik

Answer 11

you're welcome ... can you do the rest ?

Answer 12

yup

Answer 13

is expression 80*2^2

Answer 14

the 2nd one

Answer 15

\[\LARGE 80\cdot \left(2\right)^{\frac{28}{28}}= 80\cdot 2^1\]

Answer 16

yeah just got the mistake

Answer 17

so 160

Answer 18

320 is the last one

Answer 19

What does each value of the expression represent?

Answer 20

how do you mean represent?

Answer 21

nvm i got it

Answer 22

@daja2fly Remember exponents are negative. You are modeling radioactive decay, and the amount of a substance DECAYS (gets smaller) with time. So for example, 2^-2 is 1/4 so
\[ 80\cdot 2^{-2} = 80\cdot \frac{1}{4}= 20 \]
Notice that you have less of the substance.

Btw, when you evaluate an expression you do exponents before multiplication.

Answer 23

If you have a positive exponent, you have exponential GROWTH. That is what populations do, for example.

Answer 24

so will the third be -40

Answer 25

Negative exponents work differently. You have to learn new rules (which may not make much sense, but they work)

So for the third question \( 80 \cdot 2^{-\frac{56}{28}} \)
You can evaluate (simplify) -56/28 to -2
So you have
\( 80 \cdot 2^{-2} \)

Now use the rule that a NEGATIVE EXPONENT means flip:
\[ 2^{-2}= \frac{1}{2^{2}} \] and
\[ 80 \cdot \frac{1}{4} \]
This is not -40

Answer 26

the answers r 80, 40 and 20

Answer 27

Yes, do you understand how to get them?
The first means after 0 years (no time has gone by) you have what you started with
after 1 year, you have half of what you started with (that is why they call it "half-life")

Answer 28

yup