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2 years ago

The amount of a radioactive substance decreases by 10% every

Mathematics

1 answer:

uranmaximum [27]2 years ago

3 0

Answer:

Step-by-step explanation:

We would apply the formula,

y = ab^t

Where

a represents the initial amount of substance.

t represents the decay time.

From the information given

a = 100

t = 12 hours

Since after 12 hours, the amount of substance reduces by 0.1, then

y = 0.1 × 100 = 10

Therefore

10 = 100 × b^12

Dividing through by 100, it becomes

0.1 = b^12

Raising both sides of the equation by 1/12, it becomes

0.1^(1/12) = b^12/12

b = 0.8

The equation becomes

y = 100(0.8)^t

Where t = n, the expression becomes

y = 100(0.8)^n

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astra-53 [7]

$x+y=k\implies y=k-x$

Substitute this into the parabolic equation,

$k-x=6-(x-3)^2\implies x^2-7x+(k+3)=0$

We're told the line $x+y=k$ intersects $C$ twice, which means the quadratic above has two distinct real solutions. Its discriminant must then be positive, so we know

$(-7)^2-4(k+3)=49-4(k+3)>0\implies k$

We can tell from the quadratic equation that $C$ has its vertex at the point (3, 6). Also, note that

$-1\le\sin t\le1\implies3\le3+2\sin t\le5\implies3\le x\le5$

and

$-1\le\cos2t\le1\implies2\le4+2\cos2t\le6\implies2\le y\le6$

so the furthest to the right that $C$ extends is the point (5, 2). The line $x+y=k$ passes through this point for $2+5=k\implies k=7$ . For any value of $k$ , the line $x+y=k$ passes through $C$ either only once, or not at all.