Which situation is an example of an observational study?

2. Suppose (220)_b and (251)_b are the squares of consecutive integers. Determine b.

Andrei [34K]

Let $x$ and $x+1$ be these consecutive integers. For some base $b$ , we can write

$(x_{10})^2=220_b=2b^2+2b$

$((x+1)_{10})^2=251_b=2b^2+5b+1$

If

$x^2=2b^2+2b$

then

$x^2+1=2b^2+2b+1$

Now,

$x^2+2x+1=2b^2+5b+1$

$2x+2b^2+2b+1=2b^2+5b+1$

$\implies2x=3b$

Squaring both sides gives

$4x^2=9b^2$

and so

$4(2b^2+2b)=9b^2$

$\implies8b^2+8b=9b^2$

$\implies b^2-8b=0\implies\boxed{b=8}$

(because the base has to be non-zero)

3 0

3 years ago

In 17 weeks, Bruce earns $5,644 doing yard work. He earns the same amount each week. Let b stand for the amount earned each we

Marrrta [24]

5,644 / 17 = b
b = 332

4 0

2 years ago

Ooth 3 12100 Х -3 -2. у 5 2 -1 4 -7 What is the slope?

MrMuchimi

-4 that will be your answer

6 0

3 years ago

This question has several parts that must be completed sequentially. If you skip a part of the question, you will not receive an

Lapatulllka [165]

Answer:

Step-by-step explanation:

Given that there is a function of x,

$f(x) = 2sin x + 2cos x,0\leq x\leq 2\pi$

Let us find first and second derivative for f(x)

$f'(x) = 2cosx -2sinx\\f"(x) = -2sinx-2cosx$

When f'(x) =0 we have tanx = 1 and hence

a) f'(x) >0 for I and III quadrant

Hence increasing in $(0, \pi/2) U(\pi,3\pi/2)\\$

and decreasing in $(\pi/2, \pi)U(3\pi/2,2\pi)$

$x=\frac{\pi}{4}, \frac{3\pi}{4}$

$f"(\pi/4)$

Hence f has a maxima at x = pi/4 and minima at x = 3pi/4

b) Maximum value = $2sin \pi/4+2cos \pi/4 =2\sqrt{2}$

Minimum value = $2sin 3\pi/4+2cos 3\pi/4 =-2\sqrt{2}$

c)

f"(x) =0 gives tanx =-1

$x= 3\pi/4, 7\pi/4$

are points of inflection.

concave up in (3pi/4,7pi/4)

and concave down in (0,3pi/4)U(7pi/4,2pi)

3 0

3 years ago

One year had the lowest ERA (earned-run average, mean number of runs yielded per nine innings pitched) of any male pitcher at

lord [1]

Answer:

Thomas had the better year relative to their peers.

Step-by-step explanation:

The complete question is: One year Thomas had the lowest ERA (earned-run average, mean number of runs yielded per nine innings pitched) of any male pitcher at his school, with an ERA of 3.31. Also, Karla had the lowest ERA of any female pitcher at the school with an ERA of 3.02. For the males, the mean ERA was 4.837 and the standard deviation was 0.541. For the females, the mean ERA was 4.533 and the standard deviation was 0.539. Find their respective z-scores. Which player had the better year relative to their peers, or ? (Note: In general, the lower the ERA, the better the pitcher.)

We are given that for the males, the mean ERA was 4.837 and the standard deviation was 0.541. For the females, the mean ERA was 4.533 and the standard deviation was 0.539.

As, we know that the z-score is calculated by the following formula;

Z = $\frac{X-\mu}{\sigma}$ ~ N(0,1)

where, $\mu$ = population mean

$\sigma$ = standard deviation

Now, firstly we will calculate the z score for Thomas;

z-score = $\frac{X-\mu}{\sigma}$

= $\frac{3.31-4.837}{0.541}$ = -2.823

{Here, the mean ERA for the males was 4.837 and the standard deviation was 0.541}

Similarly, we will calculate the z score for Karla;

z-score = $\frac{X-\mu}{\sigma}$

= $\frac{3.02-4.533}{0.539}$ = -2.807

{Here, the mean ERA for the females was 4.533 and the standard deviation was 0.539}

Now, it is stated in the question that the lower the ERA, the better the pitcher.

So, we can clearly see that Thomas had a lower ERA of z-score as -2.823 < -2.807. This means that Thomas had the better year relative to their peers.

5 0

3 years ago