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3 years ago

The radius of a circle is 17.5. Find the exact area of the circle.

Mathematics

1 answer:

guajiro [1.7K]3 years ago

4 0

If the radius is 17.5 I believe that the area is 962.11.

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I need help putting this in corresponding factored form. I got two wrong but I’m not sure how to do it and show my work.

Anna11 [10]

Answer:

x^2-16 goes with (x+4)(x-4)

x^2+10x+16 goes with (x+8)(x+2)

Step-by-step explanation:

The first one you got wrong is known as a difference of squares.

To factor a difference of squares, a^2-b^2, you just write it as (a-b)(a+b) or (a+b)(a-b) would work too.

So x^2-16=(x-4)(x+4) or (x+4)(x-4).

Let's check (x+4)(x-4) using foil!

First: x(x)=x^2

Outer: x(-4)=-4x

Inner: 4(x)=4x

Last: 4(-4)=-16

----------------------Add

x^2-16

Bingo! (x+4)(x-4) definitely corresponds to x^2-16.

Here are more examples of factoring a difference of squares:

Example 1: x^2-25 = (x+5)(x-5)

Example 2: x^2-81 = (x+9)(x-9)

Example 3: x^2-100 =(x+10)(x-10)

Onward to the next problem:

x^2+10x+16

When the coefficient of the leading term of a quadratic is 1, all you have to do is find two numbers that multiply to be c=16 and add up be b=10.

Those numbers would be 8 and 2

because 8(2)=16 and 8+2=10.

So the factored form of x^2+10x+16 is (x+2)(x+8) or (x+8)(x+2).

Here is another example of when the leading coefficient of a quadratic is 1:

Example 1: x^2+5x+6=(x+2)(x+3) since 3(2)=6 and 3+2=5.

Example 2: x^2-x-6=(x-3)(x+2) since -3(2)=-6 and -3+2=-1.

5 0

3 years ago

A statistics professor plans classes so carefully that the lengths of her classes are uniformly distributed between 47.0 and 52.

Pavlova-9 [17]

Answer:

0.15 or 15%

Step-by-step explanation:

Since lengths are uniformly distributed, the probability that a class period runs between a two exact times is:

$P(x_1\leq x \leq x_2)=\frac{x_2-x_1}{b-a}$

In this case, a = 47.0 and b = 52.0 minutes.

The probability that a given class period runs between 50.25 and 51.0 minutes is:

$P(50.25\leq x \leq 51.0)=\frac{51.0-50.25}{52-47} \\P(50.25\leq x \leq 51.0)=0.15=15\%$

The probability is 0.15 or 15%.

7 0

3 years ago

A sample of a radioactive isotope had an initial mass of 360 mg in the year 1998 and

RUDIKE [14]

Answer:

193 mg

Step-by-step explanation:

Exponential decay formula:

$A_t = A_0e^r^t$
where Aₜ = mass at time t, A₀ = mass at time 0, r = decay constant (rate), t = time

Our known variables are:

1998 to the year 2004 is a total of t = 6 years.
The sample of radioactive isotope has an initial mass of A₀ = 360 mg at time 0 and a mass of Aₜ = 270 mg at time t.

Let's solve for the decay constant of this sample.

$270=360e^-^r^(^6^)$
$270=360e^-^6^r$
$\frac{3}{4} =e^-^6^r$
$\text{ln} (\frac{3}{4} )= \text{ln}(e^-^6^r)$
$\text{ln} (\frac{3}{4} )=-6r$
$r=-\frac{\text{ln}\frac{3}{4} }{6}$
$r=0.04794701$

Using our new variables, we can now solve for Aₜ at t = 7 years, since we go from 2004 to 2011.

Our new initial mass is A₀ = 270 mg. We solved for the decay constant, r = 0.04794701.

$A_t=270e^-^(^0^.^0^4^7^9^4^8^0^1^)^(^7^)$
$A_t=270e^-^0^.^3^3^5^6^2^9^0^7$
$A_t=193.01982213$

The expected mass of the sample in the year 2011 would be 193 mg.

3 0

2 years ago

Which of the following statements is true?

sertanlavr [38]

You didn't give the statements

3 0

3 years ago

4 is 12.5 % of a number?

guajiro [1.7K]

The answer is -32 I think

6 0

3 years ago

Read 2 more answers