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Darya [45]
3 years ago
14

The element plutonium-239 is highly radioactive. Nuclear reactors

Mathematics
1 answer:
Dominik [7]3 years ago
7 0

Answer:

2.84\cdot 10^{-5} y^{-1}

Step-by-step explanation:

The decay rate of a radioactive isotope (also called activity of the isotope) is given by:

r=k N

where

r is the decay rate

k is the decay constant

N is the number of nuclei in the radioactive sample

The decay constant of a radioactive isotope is also related to the half-life of the isotope by the formula

k=\frac{ln2}{t_{1/2}}

where

t_{1/2} is the half-life of the isotope, which is the time taken for the sample to halve, compared to its initial amount

In this problem, the half-life of plutioniun-239 is

t_{1/2}=24,360 y

Therefore, the k-factor (decay constant) is:

k=\frac{ln 2}{24,360}=2.84\cdot 10^{-5} y^{-1}

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What is the sum of 20x^2-10x-30
ivann1987 [24]

Answer:

The sum of the roots is 0.5

Step-by-step explanation:

<u><em>The correct question is</em></u>

What is the sum of the roots of 20x^2-10x-30

we know that

In a quadratic equation of the form

ax^{2} +bx+c=0

The sum of the roots is equal to

-\frac{b} {a}

in this problem we have

20x^{2} -10x-30=0  

so

a=20\\b=-10\\c=-30

substitute

-\frac{(-10)} {20}=0.5

<u><em>Verify</em></u>

Find the roots of the quadratic equation

The formula to solve a quadratic equation is equal to

x=\frac{-b\pm\sqrt{b^{2}-4ac}} {2a}

a=20\\b=-10\\c=-30

substitute

x=\frac{-(-10)\pm\sqrt{-10^{2}-4(20)(-30)}} {2(20)}

x=\frac{10\pm\sqrt{2,500}} {40}

x=\frac{10\pm50} {40}

x=\frac{10+50} {40}=1.5

x=\frac{10-50} {40}=-1

The roots are x=-1 and x=1.5

The sum of the roots are

-1+1.5=0.5 ----> is ok

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Step-by-step explanation: l

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