Answer:
The answer to your question is: I(dB) = 320
Step-by-step explanation:
Data
I(dB) = 10log(
)
I = intensity of a given sound
Io = hearing intensity
if I = 10³²(Io) find I(dB)
Process
Substitute the value of I in the equation given and simplify using logarithms rules.
l(dB) = 
Eliminate Io
I(dB) = 10 log (10³²)
Use the rule of powers in logarithms
I(dB) = 10(32)log(10)
l(dB) = 320(1)
I(dB) = 320
Consider the equation
.
First, you can use the substitution
, then
and equation becomes
. This equation is quadratic, so
.
Then you can factor this equation:
.
Use the made substitution again:
.
You have in each brackets the expression like
that is equal to
. Thus,
![x^3+5=(x+\sqrt[3]{5})(x^2-\sqrt[3]{5}x+\sqrt[3]{25}) ,\\x^3+1=(x+1)(x^2-x+1)](https://tex.z-dn.net/?f=%20x%5E3%2B5%3D%28x%2B%5Csqrt%5B3%5D%7B5%7D%29%28x%5E2-%5Csqrt%5B3%5D%7B5%7Dx%2B%5Csqrt%5B3%5D%7B25%7D%29%20%2C%5C%5Cx%5E3%2B1%3D%28x%2B1%29%28x%5E2-x%2B1%29%20%20%20)
and the equation is
.
Here
and you can sheck whether quadratic trinomials have real roots:
1.
.
2.
.
This means that quadratic trinomials don't have real roots.
Answer:
If you need complex roots, then
.
We need to call for x minute
+ Phone Company A charges a monthly fee of $42.50, and $0.02 for each minute talk time. So we have to spend: <span>$42.50+ $0.02x
+ </span>Phone company B charges a monthly fee of $25.00, and $0.09 for each minute of talk time. So we have to spend: <span>$25.00+ $0.09x
We solve for x: </span>$42.50+ $0.02x> <span>$25.00+ $0.09x
or </span>$42.50- $25.00 > $0.09x- <span>$0.02x
and we have $0.07x<$27.50
or x< 27.50:0.07 and x< 393.86
The answer is:
If we have to call much time, at least 394 minutes, we should choose A
If not, choose B</span>